Let's break this down. We're going to add 3002 and 2901 together.

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

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

Step 3: We'll start by adding the digits 0 & 9 in column 3 and get 9.

Step 4: We'll start by adding the digits 3 & 2 in column 4 and get 5.

So, 3002 + 2901 = 5903.

