Added practice exercises.

- Exercise 1: Calculate total and average marks for a class using an array of student marks (implemented using a 'for-of' loop).
- Exercise 2: Apply a 10% discount to item prices using two methods:
  - 'for-in' loop for modifying array values.
  - Traditional 'for' loop for direct index tracking and modifications.

Author: Harshitap0809

02_Basics/01_Arrays7.js

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+// Let's Practice
+// -------------------------------------------------------------------------------------------------------------------------
+
+// 1. For a given array with marks of students -> [85,97,44,76,60]. Find the average marks of the entire class.
+
+let marks = [85, 97, 44, 76, 60];
+let totalsum = 0;
+
+// Add each mark to the total
+for (let value of marks) {
+  totalsum = totalsum + value;
+}
+
+console.log(`total marks of the entire class is : ${totalsum}`);
+
+// Calculate average marks
+let avg = totalsum / marks.length;
+console.log(`total average marks of the entire class is : ${avg}`);
+
+// -------------------------------------------------------------------------------------------------------------------------
+
+// 2. For a given array with prices of 5 items -> [250,645,300,900,50] 
+// All items have an offer of 10% OFF on them. Change the array to store final price after applying the offer.
+
+// Calculation example:
+// Applying 10% off on 300 = 300/10 = 30/- off
+// Final price = 300 - 30 = 270
+// The updated array in this case value will turn out to be 270 after applying an offer of 10%.
+// conclusion: The updated array value will reflect the discounted prices.
+
+// SHOWING 2 WAYS TO SOLVE: 
+
+// 1. Using 'for-of' loop (modify the for-in loop and track the index indirectly)
+let items = [250, 645, 300, 900, 50];
+let index = 0;
+
+for (const value of items) {
+  console.log(`value at index ${index} =  ${value}`);
+  index++;
+}
+
+// 2. Using traditional 'for' loop (directly track the index)
+
+// 1. Solving the question using 'for-in' loop
+let items1 = [250, 645, 300, 900, 50];
+let index1 = 0;
+
+for (const value of items1) {
+  console.log(`value at index ${index1} =  ${value}`);
+
+  let offer = value / 10; // Calculate 10% discount
+  items1[index1] = items1[index1] - offer; // Apply discount
+  console.log(`value after offer = ${items1[index1]}`);
+
+  index1++;
+}
+console.log(items1); // Final array after discount
+
+// 2. Solving the question using traditional 'for' loop
+let items2 = [250, 645, 300, 900, 50];
+
+for (let index2 = 0; index2 < items2.length; index2++) {
+  console.log(`value at ${index2} = ${items2[index2]}`);
+
+  let offer = items2[index2] / 10; // Calculate 10% discount
+  items2[index2] = items2[index2] - offer; // Apply discount
+  console.log(`value after offer = ${items2[index2]}`);
+}
+console.log(items2); // Final array after discount
+
+// -------------------------------------------------------------------------------------------------------------------------