Let's break this down. We're going to add 263 and 8126 together.

Step 1: We'll start by adding the digits 3 & 6 in column 1 and get 9.

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

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 0 & 8 in column 4 and get 8.

So, 263 + 8126 = 8389.

