Let's break this down. We're going to add 9940 and 7015 together.

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

Step 2: We'll start by adding the digits 4 & 1 in column 2 and get 5.

Step 3: We'll start by adding the digits 9 & 0 in column 3 and get 9.

Step 4: We'll start by adding the digits 9 & 7 in column 4 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

So, 9940 + 7015 = 16955.

