Let's break this down. We're going to add 1013 and 8004 together.

Step 1: We'll start by adding the digits 3 & 4 in column 1 and get 7.

Step 2: We'll start by adding the digits 1 & 0 in column 2 and get 1.

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

Step 4: We'll start by adding the digits 1 & 8 in column 4 and get 9.

So, 1013 + 8004 = 9017.

