diff --git a/.gitignore b/.gitignore
index 936e5c57a..435be66d3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
 /node_modules/
 /package-lock.json
+.idea
+.vscode
diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index 75b3c6aab..486cdd3f3 100644
--- a/extra/1-currency-conversion.js
+++ b/extra/1-currency-conversion.js
@@ -5,7 +5,12 @@
   Write a function that converts a price to USD (exchange rate is 1.4 $ to £)
 */
 
-function convertToUSD() {}
+function convertToUSD(price) {
+  const EXCHANGE_RATE = 1.4;
+  let priceInUSD = price * EXCHANGE_RATE;
+  let priceInUSDFormatted = priceInUSD.toFixed(2)
+  return Number(priceInUSDFormatted);
+}
 
 /*
   CURRENCY CONVERSION
@@ -15,7 +20,14 @@ 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(price) {
+  const EXCHANGE_RATE = 5.7;
+  let amountInBRL = price * EXCHANGE_RATE;
+  let fee = amountInBRL * 0.01;
+  let finalAmountInBRL = amountInBRL - fee;
+  let finalAmountInBRLFormatted = finalAmountInBRL.toFixed(2);
+  return Number(finalAmountInBRLFormatted);
+}
 
 /* ======= 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..a2c5514a3 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,26 +16,29 @@
   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(num) {
+  return `£${num}`
 }
 
 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));
+//This code can be seen as bad practice because multiple methods are used in one line which makes it hard to determine the results from each methods execution. It is confusing and hard to follow.
 
 /* BETTER PRACTICE */
-
-let goodCode =
+let sum = add(startingValue, 10);
+let doubledSum = multiply(sum, 2);
+let goodCode = format(doubledSum);
 
 /* ======= 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..63dbb5338 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -45,9 +45,12 @@
 
 // This should log "The ball has shaken!"
 // and return the answer.
-function shakeBall() {
-  //Write your code in here
-}
+const veryPositive = "very positive";
+const positive = "positive";
+const negative = "negative";
+const veryNegative = "very negative";
+const allResults = [veryPositive, positive, negative, veryNegative]
+
 
 /* 
   This function should say whether the answer it is given is
@@ -58,10 +61,62 @@ function shakeBall() {
 
   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
+
+const veryPositiveAnswers = [
+  "It is certain.",
+  "It is decidedly so.",
+  "Without a doubt.",
+  "Yes - definitely.",
+  "You may rely on it.",
+];
+
+const positiveAnswers = [
+  "As I see it, yes.",
+  "Most likely.",
+  "Outlook good.",
+  "Yes.",
+  "Signs point to yes.",
+];
+
+const negativeAnswers = [
+    "Reply hazy, try again.",
+    "Ask again later.",
+    "Better not tell you now.",
+    "Cannot predict now.",
+    "Concentrate and ask again.",
+];
+
+const veryNegativeAnswers = [
+  "Don't count on it.",
+  "My reply is no.",
+  "My sources say no.",
+  "Outlook not so good.",
+  "Very doubtful.",
+];
+
+let allAnswers = [veryPositiveAnswers, positiveAnswers, negativeAnswers, veryNegativeAnswers];
+
+function findRandomIndex(max){
+  return  Math.floor(Math.random() * max);
 }
 
+function shakeBall() {
+  console.log("The ball has shaken!");
+  let num1 = findRandomIndex(4);
+  let num2 = findRandomIndex(5);
+  return allAnswers[num1][num2];
+ 
+}
+
+function checkAnswer(answer) {
+  let index; 
+  allAnswers.map((answerItem, i)=>{
+    if(answerItem.includes(answer)){
+      index = i;
+    } 
+  })
+  return allResults[index];
+}
 /* 
 ==================================
 ======= TESTS - DO NOT MODIFY =====
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index d9e004465..4d4f9655b 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,16 @@
 // 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;
-
-  return "The total is total";
+  let total = a + b;
+  return `The total is ${total}`;
 }
 
 /* 
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9eb8c8cd7..ff5b064e1 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..facc7cda4 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,16 +1,20 @@
 // Add comments to explain what this function does. You're meant to use Google!
+// Returns a random integer from 0 to 9
 function getRandomNumber() {
   return Math.random() * 10;
 }
 
 // Add comments to explain what this function does. You're meant to use Google!
+ //Concatenate strings,numbers, arrays:
 function combine2Words(word1, word2) {
-  return word1.concat(word2);
+    return word1.concat(word2);
 }
 
 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..f645f9305 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,7 +5,9 @@
   Sales tax is 20% of the price of the product.
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(price) {
+  return price * 1.2;
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +19,11 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(number) {
+  let tax = calculateSalesTax(number);
+  let taxFormatted = tax.toFixed(2)
+  return `£${taxFormatted}`
+}
 
 /* 
 ===================================================