Let's break this down. We're going to add 7173 and 1304 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 7 & 0 in column 2 and get 7.

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

Step 4: We'll start by adding the digits 7 & 1 in column 4 and get 8.

So, 7173 + 1304 = 8477.

