Let's break this down. We're going to add 1266 and 4403 together.

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

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 & 4 in column 3 and get 6.

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

So, 1266 + 4403 = 5669.

