Let's break this down. We're going to add 724 and 231 together.

Step 1: We'll start by adding the digits 4 & 1 in column 1 and get 5.

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

Step 3: We'll start by adding the digits 7 & 2 in column 3 and get 9.

So, 724 + 231 = 955.

