Let's break this down. We're going to add 5555 and 2431 together.

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

Step 2: We'll start by adding the digits 5 & 3 in column 2 and get 8.

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 & 2 in column 4 and get 7.

So, 5555 + 2431 = 7986.

