Let's break this down. We're going to add 7245 and 1220 together.

Step 1: We'll start by adding the digits 5 & 0 in column 1 and get 5.

Step 2: We'll start by adding the digits 4 & 2 in column 2 and get 6.

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

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

So, 7245 + 1220 = 8465.

