diff --git a/01-hello.rb b/01-hello.rb
index e0e7bbf..fe34e8d 100644
--- a/01-hello.rb
+++ b/01-hello.rb
@@ -5,4 +5,4 @@
 
 # ...
 
-puts "(请替换成最后的答案)"
\ No newline at end of file
+puts "Hello,#{your_name}"
diff --git a/02-variable.rb b/02-variable.rb
index a5a4753..dd37146 100644
--- a/02-variable.rb
+++ b/02-variable.rb
@@ -1,7 +1,7 @@
 # 题目: 交换 a, b 变数的值
 
-a = 1
-b = 2
+a = 2
+b = 1
 
 puts "a 是 #{a}"
 puts "b 是 #{b}"
@@ -10,4 +10,3 @@
 
 puts "a 应该是 2，现在是 #{a}"
 puts "b 应该是 1，现在是 #{b}"
-
diff --git a/03-triangle.rb b/03-triangle.rb
index fafec03..d65d5c6 100644
--- a/03-triangle.rb
+++ b/03-triangle.rb
@@ -6,6 +6,6 @@
 print "请输入直角三角形的底边，然后按 Enter: "
 b = gets
 
-# .....
+area = (a.to_i * b.to_i) / 2
 
-puts "直角三角形的面积是: _________"
\ No newline at end of file
+puts "直角三角形的面积是: #{area}"
diff --git a/04-pizzas.rb b/04-pizzas.rb
index 4c2521f..b3f89aa 100644
--- a/04-pizzas.rb
+++ b/04-pizzas.rb
@@ -6,7 +6,9 @@
 print "请输入有多少人要吃，然后按 Enter: "
 people = gets
 
-# .....
+every_one_eat = (pizzas.to_i / people.to_i).floor
 
-puts "每人可分得几片: _________ 片"
-puts "还剩下几片: _________ 片"
\ No newline at end of file
+remainder = pizzas.to_i % people.to_i
+
+puts "每人可分得几片: #{every_one_eat} 片"
+puts "还剩下几片: #{remainder} 片"
diff --git a/05-bmi.rb b/05-bmi.rb
index 67efdff..e8ef07c 100644
--- a/05-bmi.rb
+++ b/05-bmi.rb
@@ -7,11 +7,19 @@
 print "请输入您的体重(公斤)，然后按 Enter: "
 weight = gets
 
-print "请输入您的身高(厘米)，然后按 Enter: "
+print "请输入您的身高(米)，然后按 Enter: "
 height = gets
 
-# .....
+bmi = weight.to_f / (height.to_f) ** 2
 
-puts "您的 BMI 是: _________"
+if bmi < 18.5
+  result = "过轻"
+elsif bmi >= 24
+  result = "过重"
+else
+  result = "正常"
+end
 
-puts "您的 BMI 结果是: _________(过轻或正常或过重)"
\ No newline at end of file
+puts "您的 BMI 是: #{bmi}"
+
+puts "您的 BMI 结果是: #{result}"
diff --git a/06-interger-positive.rb b/06-interger-positive.rb
index a240f5f..89bb21f 100644
--- a/06-interger-positive.rb
+++ b/06-interger-positive.rb
@@ -4,7 +4,23 @@
 print "请输入一个整数，然后按 Enter: "
 x = gets
 
-# ....
+y = x.to_i
+z = y % 2
 
-puts "这个数是_____ (正数或零或负数)"
-puts "这个数是_____ (偶数或奇数)"
\ No newline at end of file
+if y == 0
+  result_1 = "零"
+elsif y < 0
+  result_1 = "负数"
+elsif y > 0
+  result_1 = "正数"
+end
+
+if z == 0
+  result_2 = "偶数"
+else
+  result_2 = "奇数"
+end
+
+
+puts "这个数是#{result_1}"
+puts "这个数是#{result_2}"
diff --git a/07-abcde.rb b/07-abcde.rb
index 5d0c8c3..ea6e1c8 100644
--- a/07-abcde.rb
+++ b/07-abcde.rb
@@ -17,6 +17,20 @@
 print "请输入一个整数z，然后按 Enter: "
 z = gets
 
-# ....
+x_i = x.to_i
+y_i = y.to_i
+z_i = z.to_i
 
-puts "结果是________(A或B或C或D或E)"
\ No newline at end of file
+ if x_i < 0
+   result = "A"
+ elsif x_i > 0 && y_i > 0 && z_i > 0
+   result = "B"
+ elsif x_i > 0 && y_i > 0 && z_i < 0
+   result = "C"
+ elsif x_i > 0 && y_i < 0 && z_i > 0
+   result = "D"
+ elsif x_i > 0 && y_i < 0 && z_i < 0
+   result = "E"
+ end
+
+puts "#{result}"
diff --git a/08-find-max.rb b/08-find-max.rb
index 9e6e643..b7dafd5 100644
--- a/08-find-max.rb
+++ b/08-find-max.rb
@@ -9,6 +9,16 @@
 print "请输入一个数字z，然后按 Enter: "
 z = gets
 
-# ....
+x_f = x.to_f
+y_f = y.to_f
+z_f = z.to_f
 
-puts "最大的数是 ________(x或y或z)"
\ No newline at end of file
+if x_f > y_f && x_f > z_f
+  result = x
+elsif y_f > x_f && y_f > z_f
+  result = y
+elsif z_f > x_f && z_f > y_f
+  result = z
+end
+
+puts "#{result}"
diff --git a/09-function.rb b/09-function.rb
index b1f922d..acc468e 100644
--- a/09-function.rb
+++ b/09-function.rb
@@ -1,7 +1,7 @@
 # 题目: 输入直角三角形的宽和高，输出三角形的面积
 
 def calculate_area(a, b)
-  # ....
+  a.to_f * b.to_f / 2
 end
 
 print "请输入直角三角形的高，然后按 Enter: "
@@ -12,4 +12,4 @@ def calculate_area(a, b)
 
 answer = calculate_area(a,b)
 
-puts "直角三角形的面积是: #{answer}"
\ No newline at end of file
+puts "直角三角形的面积是: #{answer}"
diff --git a/10-function.rb b/10-function.rb
index bb450fb..637862f 100644
--- a/10-function.rb
+++ b/10-function.rb
@@ -1,6 +1,18 @@
 # 题目: 使用者输入 x,y,z，请输出三个数中最大的数
 
 def find_max(x, y, z)
+
+  x_f = x.to_f
+  y_f = y.to_f
+  z_f = z.to_f
+
+  if x_f > y_f && x_f > z_f
+    result = x
+  elsif y_f > x_f && y_f > z_f
+    result = y
+  elsif z_f > x_f && z_f > y_f
+    result = z
+  end
 end
 
 print "请输入一个数字x，然后按 Enter: "
@@ -16,4 +28,4 @@ def find_max(x, y, z)
 
 answer = find_max(x,y,z)
 
-puts "最大的数是 #{answer}"
\ No newline at end of file
+puts "最大的数是 #{answer}"
diff --git a/11-seven.rb b/11-seven.rb
index 26c221d..afc26f9 100644
--- a/11-seven.rb
+++ b/11-seven.rb
@@ -3,7 +3,9 @@
 i = 1
 while ( i <= 100 )
 
-  # ....
+  if i % 7 == 0
+    puts i
+  end
 
   i+=1
-end
\ No newline at end of file
+end
diff --git a/12-sum-even.rb b/12-sum-even.rb
index 73879bb..5a74ad9 100644
--- a/12-sum-even.rb
+++ b/12-sum-even.rb
@@ -5,9 +5,11 @@
 
 while ( i <= 100 )
 
-  # ....
+  if i % 2 == 0
+    total += i
+  end
 
   i+=1
 end
 
-puts total
\ No newline at end of file
+puts total
diff --git a/13-nn.rb b/13-nn.rb
index ac0a43b..e4704d6 100644
--- a/13-nn.rb
+++ b/13-nn.rb
@@ -3,9 +3,13 @@
 print "请输入数字 N，然后按 Enter: "
 n = gets
 
-# while ( ... )
-#   while ( ...)
-#
-#   end
-# end
+a = 0
 
+while (a <= n.to_i)
+  b = 0
+  while (b <= n.to_i)
+    puts "#{a} x #{b} = #{a * b}"
+    b += 1
+  end
+    a += 1
+end
diff --git a/14-prime.rb b/14-prime.rb
index 8cf1692..736454a 100644
--- a/14-prime.rb
+++ b/14-prime.rb
@@ -1,7 +1,16 @@
 # 输入一个数字 N，请检查是不是质数
 
 def is_prime(n)
-# ....
+  a = 2
+  while a <= n
+    if n % a == 0
+      break
+      return false
+    else
+      return true
+    end
+    a += 1
+  end
 end
 
 print "请输入数字 N，然后按 Enter: "
diff --git a/15-guess-number.rb b/15-guess-number.rb
index 48f9dca..994b5a1 100644
--- a/15-guess-number.rb
+++ b/15-guess-number.rb
@@ -6,12 +6,18 @@
   print "请猜一个 0~99 的数字 N，然后按 Enter: "
   n = gets
 
-  #puts "太低了，再猜一次"
-  #puts "太高了，再猜一次"
+  if n.to_i >= target
+    puts "太高了，再猜一次"
+  end
+
+  if n.to_i <= target
+    puts "太低了，再猜一次"
+  end
+
 
   if n.to_i == target
     puts "恭喜猜中啦! "
     break
   end
 
-end
\ No newline at end of file
+end
diff --git a/16-array-sum.rb b/16-array-sum.rb
index 9b4910b..de3e8cb 100644
--- a/16-array-sum.rb
+++ b/16-array-sum.rb
@@ -1,11 +1,10 @@
 # 给定一阵列内含数字，输出最大值
 
 def find_max(array)
-  #....
+  array.max
 end
 
 arr = [8, 12, 36, 53, 9, 75, 3, 71, 59, 88]
 
 max = find_max(arr)
 puts "Max is #{max}" # 应该是 88
-
diff --git a/17-array-stats.rb b/17-array-stats.rb
index 0af81bb..514b382 100644
--- a/17-array-stats.rb
+++ b/17-array-stats.rb
@@ -12,9 +12,16 @@
   end
 end
 
+sum = 0
+arr.each do |i|
+  sum += i
+end
+
+average = sum / arr.size
+
 puts arr.to_s
 
-puts "总和是 _____"
-puts "平均是 _____"
-puts "最大值是 _____"
-puts "最小值是 _____"
\ No newline at end of file
+puts "总和是 #{sum}"
+puts "平均是 #{average}"
+puts "最大值是 #{arr.max}"
+puts "最小值是 #{arr.min}"
diff --git a/18-square-2.rb b/18-square-2.rb
new file mode 100644
index 0000000..499eb37
--- /dev/null
+++ b/18-square-2.rb
@@ -0,0 +1,12 @@
+# 建构一个阵列有一百个的元素，内容是 0, 1, 4, 9, 16, 25...... 每个元素是该索引的平方
+
+arr = []
+
+print "请输入数字 N，然后按 Enter: "
+n = gets.to_i
+
+(0..n).each_with_index do |i,j|
+  arr << j ** 2
+end
+
+puts arr.to_s
diff --git a/18-square.rb b/18-square.rb
index 226e1c1..6602934 100644
--- a/18-square.rb
+++ b/18-square.rb
@@ -3,8 +3,13 @@
 arr = []
 
 print "请输入数字 N，然后按 Enter: "
-n = gets
+n = gets.to_i
 
-# ...
+x = 0
 
-puts arr.to_s
\ No newline at end of file
+while x <= n
+  arr << x ** 2
+  x += 1
+end
+
+puts arr.to_s
diff --git a/19-filter.rb b/19-filter.rb
index ef7e515..a52c52b 100644
--- a/19-filter.rb
+++ b/19-filter.rb
@@ -1,9 +1,15 @@
 # 给定一阵列内含数字，输出另一个数组只包含偶数
 
 def filter_even(arr)
-  #...
+  a = []
+  arr.each do |i|
+    if i % 2 == 0
+      a << i
+    end
+  end
+  return a
 end
 
 arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
 
-puts filter_even(arr).to_s # 应该是 [68, 42, 46, 46, 86]
\ No newline at end of file
+puts filter_even(arr).to_s # 应该是 [68, 42, 46, 46, 86]
diff --git a/20-sorting.rb b/20-sorting.rb
index 5f82c08..3363e52 100644
--- a/20-sorting.rb
+++ b/20-sorting.rb
@@ -2,10 +2,16 @@
 # Hint: 可用 arr.sort 排序，和 arr.uniq 去除重复
 
 def filter_even(arr)
-  #...
+  a = []
+  arr.each do |i|
+    if i % 2 == 0
+      a << i
+    end
+  end
+  return a
 end
 
 arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
 
 
-puts "________" # 应该是 [42, 46, 68, 86]
\ No newline at end of file
+puts "#{filter_even(arr).uniq.sort}" # 应该是 [42, 46, 68, 86]
diff --git a/21-selection-sort.rb b/21-selection-sort.rb
index e5e7eae..80bf167 100644
--- a/21-selection-sort.rb
+++ b/21-selection-sort.rb
@@ -2,11 +2,16 @@
 # https://zh.wikipedia.org/wiki/选择排序
 
 def selection_sort(arr)
-  #...
+  ans = []
+  while arr.size > 0
+    ans << arr.min
+    arr.delete(arr.min)
+  end
+    ans
 end
 
 arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
 
 answer = selection_sort(arr)
 
-puts answer.to_s # 应该是 [1, 7, 9, 42, 46, 46, 68, 77, 86, 91]
\ No newline at end of file
+puts answer.to_s # 应该是 [1, 7, 9, 42, 46, 46, 68, 77, 86, 91]
diff --git a/22-missing.rb b/22-missing.rb
index 6898714..ec0368c 100644
--- a/22-missing.rb
+++ b/22-missing.rb
@@ -1,7 +1,8 @@
 # 给定一阵列内含数字，请输出 0~9 中不见的数字
 
 def find_missing(arr)
-  # ...
+  a = (0..9).to_a
+  a - arr.uniq
 end
 
 answer = find_missing( [2,2,1,5,8,4] )
diff --git a/23-hash-max.rb b/23-hash-max.rb
index 6fb227e..73132cc 100644
--- a/23-hash-max.rb
+++ b/23-hash-max.rb
@@ -1,7 +1,7 @@
 # 给定一 Hash，输出有最大 value 的 key
 
 def find_max(hash)
-  # ...
+  hash.key(hash.values.max)
 end
 
 h = {
@@ -15,5 +15,3 @@ def find_max(hash)
 answer = find_max(h)
 
 puts "有最大 value 的是 #{answer}" # 应该是 d
-
-
diff --git a/24-hash-even.rb b/24-hash-even.rb
index 9da9605..16c8732 100644
--- a/24-hash-even.rb
+++ b/24-hash-even.rb
@@ -1,9 +1,13 @@
 # 给定一 Hash，输出 value 是偶数的 keys
 
 def find_even_keys(hash)
-
-  # ... (请回传一个数组)
-
+  ans = []
+   hash.values.each do |i|
+     if i % 2 == 0
+       ans << hash.key(i)
+     end
+   end
+   ans
 end
 
 h = {
@@ -17,5 +21,3 @@ def find_even_keys(hash)
 answer = find_even_keys(h)
 
 puts "有偶数 value 的 keys 有 #{answer}" # 应该是数组 [b,d,e]
-
-
diff --git a/25-hash-count.rb b/25-hash-count.rb
index 2167335..478d561 100644
--- a/25-hash-count.rb
+++ b/25-hash-count.rb
@@ -4,7 +4,8 @@ def count(arr)
   h = {}
 
   arr.each do |i|
-    # ...
+    c = arr.count(i)
+    h[i] = c
   end
 
   return h # 回传一个 hash
@@ -15,4 +16,3 @@ def count(arr)
 answer = count(arr)
 
 puts answer # 答案应该是 {"a"=>3, "d"=>6, "c"=>5, "b"=>1, "e"=>5}
-
diff --git a/26-hash-filter.rb b/26-hash-filter.rb
index 51ade64..65bcbaf 100644
--- a/26-hash-filter.rb
+++ b/26-hash-filter.rb
@@ -7,10 +7,17 @@
   { "name" => "Steven", "age" => 22 },
   { "name" => "Vincent", "age" => 6 },
 ]
+person = []
 
-# ....
+arr.each do |i|
+  if i["age"] >= 18
+    person << i
+  end
+end
 
-puts "所有成年人，并由小到大: _________"
+result = person.sort_by {|a| a["age"]}
+
+puts "所有成年人，并由小到大: #{result}"
 
 # 答案应该是
 #[
diff --git a/27-class.rb b/27-class.rb
index 8cec2c9..5882a91 100644
--- a/27-class.rb
+++ b/27-class.rb
@@ -1,5 +1,9 @@
 class Person
-  # ...
+  attr_accessor :first_name, :last_name
+
+  def greet
+    puts "Hi,#{@first_name} #{@last_name}"
+  end
 end
 
 p1 = Person.new
@@ -11,6 +15,3 @@ class Person
 p2.first_name = "William"
 p2.last_name = "Zhang"
 p2.greet # 输出 "Hello, William Zhang"
-
-
-
diff --git a/28-word-count.rb b/28-word-count.rb
index 2643123..6ae41ba 100644
--- a/28-word-count.rb
+++ b/28-word-count.rb
@@ -2,4 +2,15 @@
 
 doc = File.read("wordcount.txt")
 
-# ...
+cut_doc = doc.downcase.scan(/\w+/)
+
+words = cut_doc.uniq
+
+result = {}
+
+words.each do |i|
+  a = cut_doc.count(i)
+  result[i] = a
+end
+
+ puts result
diff --git a/29-todos.rb b/29-todos.rb
index 0bddde2..32b92cb 100644
--- a/29-todos.rb
+++ b/29-todos.rb
@@ -15,19 +15,27 @@
   print "请输入指令 1. add 2. remove 3. save，然后按 Enter: "
   command = gets.chomp
 
-  if command == "add"
+  if command == "1"
     print "请输入代办事项: "
-    # ...
-  elsif command == "remove"
+    todos << gets.chomp
+  elsif command == "2"
     print "请输入要删除的编号: "
-    # ...
-  elsif command == "save"
+    ind = gets.to_i
+    todos.delete_at(ind)
+  elsif command == "3"
     puts "存盘离开"
+    File.open("todos.txt","w+") do |f|
+      todos.each do |i|
+        f << i
+        f << "\n"
+      end
+    end
 
-    # ...
+    todos.each_with_index do |todo, index|
+      puts "#{index}: #{todo}"
+    end
     break;
   else
     puts "看不懂，请再输入一次"
   end
 end
-
diff --git a/todos.tex b/todos.tex
new file mode 100644
index 0000000..faa982d
--- /dev/null
+++ b/todos.tex
@@ -0,0 +1,5 @@
+Buy book
+Go Shopping
+Walk
+Gogo
+add01
diff --git a/todos.txt b/todos.txt
index 4757e85..4bd72ec 100644
--- a/todos.txt
+++ b/todos.txt
@@ -2,3 +2,5 @@ Buy book
 Go Shopping
 Walk
 Gogo
+add01
+add02