Let's break this down. We're going to add 7263 and 603 together.

Step 1: We'll start by adding the digits 3 & 3 in column 1 and get 6.

Step 2: We'll start by adding the digits 6 & 0 in column 2 and get 6.

Step 3: We'll start by adding the digits 2 & 6 in column 3 and get 8.

Step 4: We'll start by adding the digits 7 & 0 in column 4 and get 7.

So, 7263 + 603 = 7866.

