Let's break this down. We're going to add 2818 and 1131 together.

Step 1: We'll start by adding the digits 8 & 1 in column 1 and get 9.

Step 2: We'll start by adding the digits 1 & 3 in column 2 and get 4.

Step 3: We'll start by adding the digits 8 & 1 in column 3 and get 9.

Step 4: We'll start by adding the digits 2 & 1 in column 4 and get 3.

So, 2818 + 1131 = 3949.

