Let's break this down. We're going to add 123 and 4173 together.

Step 1: We'll start by adding the digits 3 & 3 in column 1 and get 6.

Step 2: We'll start by adding the digits 2 & 7 in column 2 and get 9.

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

Step 4: We'll start by adding the digits 0 & 4 in column 4 and get 4.

So, 123 + 4173 = 4296.

