Let's break this down. We're going to add 131 and 2408 together.

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

Step 2: We'll start by adding the digits 3 & 0 in column 2 and get 3.

Step 3: We'll start by adding the digits 1 & 4 in column 3 and get 5.

Step 4: We'll start by adding the digits 0 & 2 in column 4 and get 2.

So, 131 + 2408 = 2539.

