Let's break this down. We're going to add 5115 and 1312 together.

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

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

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

Step 4: We'll start by adding the digits 5 & 1 in column 4 and get 6.

So, 5115 + 1312 = 6427.

