Let's break this down. We're going to add 6243 and 1115 together.

Step 1: We'll start by adding the digits 3 & 5 in column 1 and get 8.

Step 2: We'll start by adding the digits 4 & 1 in column 2 and get 5.

Step 3: We'll start by adding the digits 2 & 1 in column 3 and get 3.

Step 4: We'll start by adding the digits 6 & 1 in column 4 and get 7.

So, 6243 + 1115 = 7358.

