diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index 75b3c6aab..301ec3837 100644
--- a/extra/1-currency-conversion.js
+++ b/extra/1-currency-conversion.js
@@ -5,7 +5,10 @@
   Write a function that converts a price to USD (exchange rate is 1.4 $ to £)
 */
 
-function convertToUSD() {}
+function convertToUSD(amount) {
+  let rate = 1.4;
+  return amount * rate;
+}
 
 /*
   CURRENCY CONVERSION
@@ -15,7 +18,10 @@ function convertToUSD() {}
   They have also decided that they should add a 1% fee to all foreign transactions, which means you only convert 99% of the £ to BRL.
 */
 
-function convertToBRL() {}
+function convertToBRL(amount) {
+  let rate = 5.7;
+  return parseFloat((amount * 5.7 * 0.99).toFixed(2));
+}
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
diff --git a/extra/2-piping.js b/extra/2-piping.js
index b4f8c4c1b..9a05ef9e4 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,26 +16,30 @@
   the final result to the variable goodCode
 */
 
-function add() {
-
+function add(a, b) {
+  return a + b;
 }
 
-function multiply() {
-
+function multiply(a, b) {
+    return a * b;
 }
 
-function format() {
-
+function format(value) {
+  let currency = "£"
+   return "£" + value;
 }
 
 const startingValue = 2;
 
 // Why can this code be seen as bad practice? Comment your answer.
-let badCode =
+let badCode = format(multiply(add(startingValue, 10), 2));
 
 /* BETTER PRACTICE */
 
-let goodCode =
+let sum = add(startingValue, 10);
+let multiplies = multiply(sum , 2);
+let goodCode = format(multiplies);
+// let goodCode
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
diff --git a/extra/3-magic-8-ball.js b/extra/3-magic-8-ball.js
index 46f65f928..ff4f6a61f 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -14,52 +14,73 @@
 
   Below are the possible answers:
 
-  ## Very positive
-    It is certain.
-    It is decidedly so.
-    Without a doubt.
-    Yes - definitely.
-    You may rely on it.
-
-  ## Positive
-    As I see it, yes.
-    Most likely.
-    Outlook good.
-    Yes.
-    Signs point to yes.
-
-  ## Negative
-    Reply hazy, try again.
-    Ask again later.
-    Better not tell you now.
-    Cannot predict now.
-    Concentrate and ask again.
-
-  ## Very negative
-    Don't count on it.
-    My reply is no.
-    My sources say no.
-    Outlook not so good.
-    Very doubtful.
-*/
+  **/
+
+  let veryPositive = [
+    "It is certain.",
+    "It is decidedly so.",
+    "Without a doubt.",
+    "Yes - definitely.",
+    "You may rely on it.",
+  ]
+    
+
+  let Positive = [
+    "As I see it, yes.",
+    "Most likely.",
+    "Outlook good.",
+    "Yes.",
+    "Signs point to yes."
+  ]
+   
+
+  let Negative =[
+    "Reply hazy, try again.",
+    "Ask again later.",
+    "Better not tell you now.",
+    "Cannot predict now.",
+    "Concentrate and ask again."
+  ]
+   
+
+  let veryNegative = [
+    "Don't count on it.",
+    "My reply is no.",
+    "My sources say no.",
+    "Outlook not so good.",
+    "Very doubtful."
+  ]
 
 // This should log "The ball has shaken!"
 // and return the answer.
 function shakeBall() {
-  //Write your code in here
+  console.log("The ball has shaken!");
+  let randomIndex = Math.floor(Math.random() * allAnswers.length);
+  return allAnswers[randomIndex];
 }
 
-/* 
-  This function should say whether the answer it is given is
-    - very positive
-    - positive
-    - negative
-    - very negative
 
-  This function should expect to be called with any value which was returned by the shakeBall function.
-*/
+  //This function should say whether the answer it is given is
+  let allAnswers =[
+    ...veryPositive,
+    ...Positive,
+    ...Negative,
+    ...veryNegative,
+  ]
+   
+
+  //This function should expect to be called with any value which was returned by the shakeBall function.
+
 function checkAnswer(answer) {
-  //Write your code in here
+  if(veryPositive.includes(answer)){
+    return "very positive";
+  } else if (Positive.includes(answer)){
+    return "Positive";
+  } else if (Negative.includes(answer)){
+    return "Negative";
+  } else if(veryNegative.includes(answer)){
+    return "very negative";
+  } 
 }
 
 /* 
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index d9e004465..e270488d8 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,17 @@
 // There are syntax errors in this code - can you fix it to pass the tests?
 
-function addNumbers(a b c) {
+function addNumbers(a, b, c) {
   return a + b + c;
 }
 
-function introduceMe(name, age)
-  return `Hello, my {name}` is "and I am $age years old`;
+function introduceMe(name, age){
+  return `Hello, my name is ${name} and I am ${age} years old`;
+}
 
 function getTotal(a, b) {
-  total = a ++ b;
+  total = a + b;
 
-  return "The total is total";
+  return `The total is ${total}`;
 }
 
 /* 
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9eb8c8cd7..560a40813 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,15 @@
 // The syntax for these functions is valid but there are some errors, find them and fix them
 
 function trimWord(word) {
-  return wordtrim();
+  return word.trim();
 }
 
 function getStringLength(word) {
-  return "word".length();
+  return word.length;
 }
 
 function multiply(a, b, c) {
-  a * b * c;
-  return;
+  return a * b * c; 
 }
 
 /* 
diff --git a/mandatory/3-function-output.js b/mandatory/3-function-output.js
index 5a953ba60..a78db8c52 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,16 +1,17 @@
 // Add comments to explain what this function does. You're meant to use Google!
 function getRandomNumber() {
   return Math.random() * 10;
+   // Math.random generate a number between 1 to 10. That is not a whole number nor 1. In order to get a whole number multiply your answer to 10: Math.random() * 10
 }
 
 // Add comments to explain what this function does. You're meant to use Google!
 function combine2Words(word1, word2) {
   return word1.concat(word2);
+  // this function combine two strings and make a new string.
 }
 
 function concatenate(firstWord, secondWord, thirdWord) {
-  // Write the body of this function to concatenate three words together.
-  // Look at the test case below to understand what this function is expected to return.
+  return firstWord.concat(' ',secondWord, ' ',thirdWord,);
 }
 
 /* 
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..0c433b943 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,7 +5,11 @@
   Sales tax is 20% of the price of the product.
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(price) {
+  let salesTax = price * 0.2;
+  let productPrice = price + salesTax;
+  return productPrice;
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +21,10 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(price) {
+  let productPrice = calculateSalesTax(price);
+  return "£" + productPrice.toFixed(2);
+}
 
 /* 
 ===================================================
diff --git a/package.json b/package.json
index 26f46e540..22faa0546 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,7 @@
   "description": "Exercises for JS1 Week 1",
   "license": "CC-BY-SA-4.0",
   "scripts": {
-    "test": "jest"
+    "test": "jest --watchAll --verbose"
   },
   "repository": {
     "type": "git",