Let's break this down. We're going to add 5106 and 1303 together.

Step 1: We'll start by adding the digits 6 & 3 in column 1 and get 9.

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

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, 5106 + 1303 = 6409.

