Let's break this down. We're going to add 9615 and 1800 together.

Step 1: We'll start by adding the digits 5 & 0 in column 1 and get 5.

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 6 & 8 in column 3 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 9 & 1 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 9615 + 1800 = 11415.

