Let's break this down. We're going to add 1201 and 7588 together.

Step 1: We'll start by adding the digits 1 & 8 in column 1 and get 9.

Step 2: We'll start by adding the digits 0 & 8 in column 2 and get 8.

Step 3: We'll start by adding the digits 2 & 5 in column 3 and get 7.

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

So, 1201 + 7588 = 8789.

