Let's break this down. We're going to add 1261 and 80 together.

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

Step 2: We'll start by adding the digits 6 & 8 in column 2 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 2 & 0 in column 3 and get 3.

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

So, 1261 + 80 = 1341.

