Let's break this down. We're going to add 521 and 1306 together.

Step 1: We'll start by adding the digits 1 & 6 in column 1 and get 7.

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

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

Step 4: We'll start by adding the digits 0 & 1 in column 4 and get 1.

So, 521 + 1306 = 1827.

