Let's break this down. We're going to add 6121 and 1031 together.

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

Step 2: We'll start by adding the digits 2 & 3 in column 2 and get 5.

Step 3: We'll start by adding the digits 1 & 0 in column 3 and get 1.

Step 4: We'll start by adding the digits 6 & 1 in column 4 and get 7.

So, 6121 + 1031 = 7152.

