Let's break this down. We're going to add 1504 and 3104 together.

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

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 5 & 1 in column 3 and get 6.

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

So, 1504 + 3104 = 4608.

