diff --git a/01-hello.rb b/01-hello.rb
index e0e7bbf..36af2aa 100644
--- a/01-hello.rb
+++ b/01-hello.rb
@@ -1,8 +1,9 @@
 # 题目: 输入名字，输出 "Hello, 名字"
 
 print "请输入你的名字，然后按 Enter: "
+
 your_name = gets
 
 # ...
 
-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..cb64515 100644
--- a/02-variable.rb
+++ b/02-variable.rb
@@ -2,6 +2,10 @@
 
 a = 1
 b = 2
+c = a
+a = b
+b = c
+
 
 puts "a 是 #{a}"
 puts "b 是 #{b}"
@@ -10,4 +14,3 @@
 
 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..b9139be 100644
--- a/03-triangle.rb
+++ b/03-triangle.rb
@@ -6,6 +6,7 @@
 print "请输入直角三角形的底边，然后按 Enter: "
 b = gets
 
+c = a.to_f * b.to_f / 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: #{c}"
diff --git a/04-pizzas.rb b/04-pizzas.rb
index 4c2521f..2425da0 100644
--- a/04-pizzas.rb
+++ b/04-pizzas.rb
@@ -6,7 +6,10 @@
 print "请输入有多少人要吃，然后按 Enter: "
 people = gets
 
+a = pizzas.to_f / people.to_i
+
+b = pizzas.to_f % people.to_i
 # .....
 
-puts "每人可分得几片: _________ 片"
-puts "还剩下几片: _________ 片"
\ No newline at end of file
+puts "每人可分得几片: #{a.floor} 片"
+puts "还剩下几片: #{b} 片"
diff --git a/05-bmi.rb b/05-bmi.rb
index 67efdff..7170dad 100644
--- a/05-bmi.rb
+++ b/05-bmi.rb
@@ -10,8 +10,18 @@
 print "请输入您的身高(厘米)，然后按 Enter: "
 height = gets
 
+bmi = weight.to_f/(height.to_f * height.to_f)*10000
+
+if bmi < 18.5
+  result = "过轻"
+elsif bmi >= 24
+  result = "过重"
+else
+  result = "正常"
+end
+
 # .....
 
-puts "您的 BMI 是: _________"
+puts "您的 BMI 是: #{bmi}"
 
-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 结果是: #{result}"
diff --git a/06-interger-positive.rb b/06-interger-positive.rb
index a240f5f..a6de34c 100644
--- a/06-interger-positive.rb
+++ b/06-interger-positive.rb
@@ -3,8 +3,28 @@
 
 print "请输入一个整数，然后按 Enter: "
 x = gets
+y = x.to_i
+
+if y > 0
+  a = "正数"
+  if y%2 == 0
+    b = "偶数"
+  else
+    b = "奇数"
+  end
+elsif y == 0
+  a = "零"
+  b = "偶数"
+else
+  a = "负数"
+  if y%2 == 0
+    b = "偶数"
+  else
+    b = "奇数"
+  end
+end
 
 # ....
 
-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
+puts "这个数是 #{a} "
+puts "这个数是 #{b} "
diff --git a/07-abcde.rb b/07-abcde.rb
index 5d0c8c3..b94f6f8 100644
--- a/07-abcde.rb
+++ b/07-abcde.rb
@@ -10,13 +10,28 @@
 
 print "请输入一个整数x，然后按 Enter: "
 x = gets
+x = x.to_i
 
 print "请输入一个整数y，然后按 Enter: "
 y = gets
+y = y.to_i
 
 print "请输入一个整数z，然后按 Enter: "
 z = gets
+z = z.to_i
+
+if x < 0
+  a = "A"
+elsif ( y > 0 ) && ( z > 0 )
+  a = "B"
+elsif ( y > 0 ) && ( z < 0 )
+  a = "C"
+elsif ( y < 0 ) && ( z > 0 )
+  a = "D"
+elsif ( y < 0 ) && ( z < 0 )
+  a = "E"
+end
 
 # ....
 
-puts "结果是________(A或B或C或D或E)"
\ No newline at end of file
+puts "结果是 #{a}"
diff --git a/08-find-max.rb b/08-find-max.rb
index 9e6e643..f523bea 100644
--- a/08-find-max.rb
+++ b/08-find-max.rb
@@ -2,13 +2,24 @@
 
 print "请输入一个数字x，然后按 Enter: "
 x = gets
+x = x.to_i
 
 print "请输入一个数字y，然后按 Enter: "
 y = gets
+y = y.to_i
 
 print "请输入一个数字z，然后按 Enter: "
 z = gets
+z = z.to_i
+
+if (x > y) && (x > z)
+  a = x
+elsif (y > z) || (y == z)
+  a = y
+else
+  a = z
+end
 
 # ....
 
-puts "最大的数是 ________(x或y或z)"
\ No newline at end of file
+puts "最大的数是 #{a}"
diff --git a/09-function.rb b/09-function.rb
index b1f922d..fffbed6 100644
--- a/09-function.rb
+++ b/09-function.rb
@@ -1,7 +1,9 @@
 # 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 = a.to_f
+  b = b.to_f
+  a * b / 2
 end
 
 print "请输入直角三角形的高，然后按 Enter: "
@@ -12,4 +14,4 @@ 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..496f847 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 = x.to_f
+  y = y.to_f
+  z = z.to_f
+  if (x > y) && (x > z)
+    a = x
+  elsif (y > z) || (y == z)
+    a = y
+  else
+    a = z
+  end
+
+  return a 
 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..6534767 100644
--- a/13-nn.rb
+++ b/13-nn.rb
@@ -2,10 +2,22 @@
 
 print "请输入数字 N，然后按 Enter: "
 n = gets
+n = n.to_i
+a = 0
+b = 0
+
+while a <= n
+  while b <= n
+    total = a * b
+    puts "#{a} x #{b} = #{total}"
+    b += 1
+  end
+  a += 1
+  b = 0
+end
 
 # while ( ... )
 #   while ( ...)
 #
 #   end
 # end
-
diff --git a/14-prime.rb b/14-prime.rb
index 8cf1692..f94bbac 100644
--- a/14-prime.rb
+++ b/14-prime.rb
@@ -1,7 +1,9 @@
 # 输入一个数字 N，请检查是不是质数
 
 def is_prime(n)
-# ....
+  if (n == 2) || ( (n > 2) && ( n % 2 != 0) )
+    return true
+  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..f9e5456 100644
--- a/15-guess-number.rb
+++ b/15-guess-number.rb
@@ -6,12 +6,17 @@
   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 "太低了，再猜一次"
+  end
+
+  if n.to_i > target
+    puts "太高了，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..91e4c91 100644
--- a/17-array-stats.rb
+++ b/17-array-stats.rb
@@ -12,9 +12,14 @@
   end
 end
 
+total = 0
+arr.each do |i|
+  total += i
+end
+
 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 #{total}"
+puts "平均是 #{total/arr.size}"
+puts "最大值是 #{arr.max}"
+puts "最小值是 #{arr.min}"
diff --git a/18-square.rb b/18-square.rb
index 226e1c1..d26ea81 100644
--- a/18-square.rb
+++ b/18-square.rb
@@ -4,7 +4,16 @@
 
 print "请输入数字 N，然后按 Enter: "
 n = gets
+n = n.to_i
+while (true)
+  if n >=0
+    arr << (n * n)
+    n -= 1
+  else
+    break
+  end
+end
 
-# ...
+arr = arr.reverse!
 
-puts arr.to_s
\ No newline at end of file
+puts arr.to_s
diff --git a/19-filter.rb b/19-filter.rb
index ef7e515..111b69e 100644
--- a/19-filter.rb
+++ b/19-filter.rb
@@ -1,9 +1,17 @@
 # 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)
-  #...
+  group = []
+
+  arr.each do |i|
+    if (i % 2 == 0 )
+      group << i
+    end
+  end
+
+  return group
 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..3ec5659 100644
--- a/20-sorting.rb
+++ b/20-sorting.rb
@@ -2,10 +2,10 @@
 # Hint: 可用 arr.sort 排序，和 arr.uniq 去除重复
 
 def filter_even(arr)
-  #...
+  arr.uniq.sort
 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).to_s # 应该是 [42, 46, 68, 86]
diff --git a/21-selection-sort.rb b/21-selection-sort.rb
index e5e7eae..67da61a 100644
--- a/21-selection-sort.rb
+++ b/21-selection-sort.rb
@@ -2,11 +2,25 @@
 # https://zh.wikipedia.org/wiki/选择排序
 
 def selection_sort(arr)
-  #...
+  n = arr.length
+  loop do
+    swapped = false
+
+    (n-1).times do |i|
+      if arr[i] > arr[i+1]
+        arr[i], arr[i+1] = arr[i+1], arr[i]
+        swapped = true
+      end
+    end
+
+    break if not swapped
+  end
+
+  arr
 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..ce011b8 100644
--- a/22-missing.rb
+++ b/22-missing.rb
@@ -1,7 +1,14 @@
 # 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, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+  arr.uniq.each do |i|
+    if a.include?(i)
+      a.delete(i)
+      a
+    end
+  end
+  return a
 end
 
 answer = find_missing( [2,2,1,5,8,4] )
diff --git a/23-hash-max.rb b/23-hash-max.rb
index 6fb227e..c2b4976 100644
--- a/23-hash-max.rb
+++ b/23-hash-max.rb
@@ -1,7 +1,8 @@
 # 给定一 Hash，输出有最大 value 的 key
 
 def find_max(hash)
-  # ...
+  x = hash.values.max
+  hash.key(x)
 end
 
 h = {
@@ -15,5 +16,3 @@ 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..5ac0807 100644
--- a/24-hash-even.rb
+++ b/24-hash-even.rb
@@ -1,7 +1,15 @@
 # 给定一 Hash，输出 value 是偶数的 keys
 
 def find_even_keys(hash)
+  array = []
 
+  hash.each do |key, value|
+    if value % 2 == 0
+      array << key
+    end
+  end
+
+  array
   # ... (请回传一个数组)
 
 end
@@ -17,5 +25,3 @@ 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..fa251de 100644
--- a/25-hash-count.rb
+++ b/25-hash-count.rb
@@ -4,7 +4,11 @@ def count(arr)
   h = {}
 
   arr.each do |i|
-    # ...
+    key = i
+    value = arr.count(i)
+    if !h.keys.include? i
+      h[key] = value
+    end 
   end
 
   return h # 回传一个 hash
@@ -15,4 +19,3 @@ 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..69308a0 100644
--- a/26-hash-filter.rb
+++ b/26-hash-filter.rb
@@ -8,9 +8,29 @@
   { "name" => "Vincent", "age" => 6 },
 ]
 
-# ....
+def filter(arr)
+  x = []
+  arr.each do |i|
+    if i["age"] >= 18
+      x << i
+    end
+  end
 
-puts "所有成年人，并由小到大: _________"
+  n = x.length-1
+  loop do
+    swapped = false
+    n.times do |s|
+      if (x[s]["age"]) > (x[s+1]["age"])
+        x[s], x[s+1] = x[s+1], x[s]
+        swapped = true
+      end
+    end
+    break if not swapped
+  end
+  x
+end
+
+puts "所有成年人，并由小到大: #{filter(arr).to_s} "
 
 # 答案应该是
 #[
diff --git a/27-class.rb b/27-class.rb
index 8cec2c9..bd125e0 100644
--- a/27-class.rb
+++ b/27-class.rb
@@ -1,5 +1,10 @@
 class Person
-  # ...
+  attr_accessor :first_name
+  attr_accessor :last_name
+
+  def greet
+    puts "Hello, #{@first_name} #{@last_name} "
+  end
 end
 
 p1 = Person.new
@@ -11,6 +16,3 @@ 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..8c50da4 100644
--- a/28-word-count.rb
+++ b/28-word-count.rb
@@ -2,4 +2,32 @@
 
 doc = File.read("wordcount.txt")
 
-# ...
+arr = doc.downcase.gsub(/[,.]/, '').split(" ")
+
+def count(arr)
+  h = {}
+
+  arr.each do |i|
+    key = i
+    value = arr.count(i)
+    if !h.keys.include? i
+      h[key] = value
+    end
+  end
+
+  return h # 回传一个 hash
+end
+
+answer = count(arr).sort
+
+answer.each do |k, v|
+  puts "#{k} #{v}"
+end
+
+#  word.each do |i|
+#    key = i
+#    value = word.count(i)
+#    if !h.keys.include? i
+#      h[key] = value
+#    end
+#  end
diff --git a/29-todos.rb b/29-todos.rb
index 0bddde2..b28dd7d 100644
--- a/29-todos.rb
+++ b/29-todos.rb
@@ -17,17 +17,21 @@
 
   if command == "add"
     print "请输入代办事项: "
-    # ...
+    todos << gets.chomp
   elsif command == "remove"
     print "请输入要删除的编号: "
-    # ...
+    todos.delete_at(gets.chomp.to_i)
   elsif command == "save"
     puts "存盘离开"
 
-    # ...
+    File.open("todos.txt", "w+") do |f|
+      todos.each do |i|
+        f << i
+        f << "\n"
+      end
+    end
     break;
   else
     puts "看不懂，请再输入一次"
   end
 end
-
diff --git a/todos.txt b/todos.txt
index 4757e85..595adbc 100644
--- a/todos.txt
+++ b/todos.txt
@@ -1,4 +1,3 @@
 Buy book
-Go Shopping
-Walk
-Gogo
+Go shopping
+Reading