diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index a10cc9ac2..fc84837e4 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,40 +1,31 @@
 // 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 " + name "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";
+  total = a + b;
+  return "The total is " + total;
 }
-
 /* 
 ===================================================
 ======= TESTS - DO NOT MODIFY BELOW THIS LINE =====
-
 There are some Tests in this file that will help you work out if your code is working.
-
 To run the tests for just this one file, type `npm test -- --testPathPattern 1-syntax-errors` into your terminal
 (Reminder: You must have run `npm install` one time before this will work!)
-
 ===================================================
 */
-
 test("addNumbers adds numbers correctly", () => {
   expect(addNumbers(3, 4, 6)).toEqual(13);
 });
-
 test("introduceMe function returns the correct string", () => {
   expect(introduceMe("Sonjide", 27)).toEqual(
     "Hello, my name is Sonjide and I am 27 years old"
   );
 });
-
 test("getTotal returns a string describing the total", () => {
   expect(getTotal(23, 5)).toEqual("The total is 28");
 });
+
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9cca7603b..fba446374 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,15 @@
 // The syntax for this function is valid but it has an error, find it and fix it.
 
 function trimWord(word) {
-  return wordtrim();
+  return trimWord();
 }
 
 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..92c75fa62 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -3,16 +3,25 @@ function getRandomNumber() {
   return Math.random() * 10;
 }
 
+//This fuction gets one random integer number by using Math library. And then multiply this number by 10
+
 // Add comments to explain what this function does. You're meant to use Google!
 function combine2Words(word1, word2) {
   return word1.concat(word2);
 }
 
+// This funtion combines the text word1 and word2
+
 function concatenate(firstWord, secondWord, thirdWord) {
+  return firstWord.concat(secondWord.concat(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.
 }
 
+// These function combines the firstWord, secondWord and thirdWord
+// Combining integers are also possible
+let x = concatenate("s", "a", "e");
+console.log(x);
 /* 
 ===================================================
 ======= TESTS - DO NOT MODIFY BELOW THIS LINE =====
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..53ef30a63 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*(20/100);
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,8 +19,10 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
-
+function addTaxAndFormatCurrency(price) {
+  return (price+(price*20/100)).toFixed(2);
+}
+console.log(addTaxAndFormatCurrency(50) + " £");
 /* 
 ===================================================
 ======= TESTS - DO NOT MODIFY BELOW THIS LINE =====
diff --git a/mandatory/index.html b/mandatory/index.html
new file mode 100644
index 000000000..def0952f9
--- /dev/null
+++ b/mandatory/index.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta http-equiv="X-UA-Compatible" content="IE=edge">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Document</title>
+</head>
+<body>
+    <script src="./3-function-output.js"></script>
+    <script src="./4-tax.js"></script>
+
+</body>
+</html>
\ No newline at end of file