Let's break this down. We're going to add 7290 and 700 together.

Step 1: We'll start by adding the digits 0 & 0 in column 1 and get 0.

Step 2: We'll start by adding the digits 9 & 0 in column 2 and get 9.

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

Step 4: We'll start by adding the digits 7 & 0 in column 4 and get 7.

So, 7290 + 700 = 7990.

