Let's break this down. We're going to add 5512 and 400 together.

Step 1: We'll start by adding the digits 2 & 0 in column 1 and get 2.

Step 2: We'll start by adding the digits 1 & 0 in column 2 and get 1.

Step 3: We'll start by adding the digits 5 & 4 in column 3 and get 9.

Step 4: We'll start by adding the digits 5 & 0 in column 4 and get 5.

So, 5512 + 400 = 5912.

