Let's break this down. We're going to add 7112 and 1245 together.

Step 1: We'll start by adding the digits 2 & 5 in column 1 and get 7.

Step 2: We'll start by adding the digits 1 & 4 in column 2 and get 5.

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

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

So, 7112 + 1245 = 8357.

