Let's break this down. We're going to add 15 and 731 together.

Step 1: We'll start by adding the digits 5 & 1 in column 1 and get 6.

Step 2: We'll start by adding the digits 1 & 3 in column 2 and get 4.

Step 3: We'll start by adding the digits 0 & 7 in column 3 and get 7.

So, 15 + 731 = 746.

