We have numbers 204 and 515. Let's start adding them together.

Step 1: We'll start by adding the digits 4 & 5 in column 1 and get 9.

Step 2: We'll start by adding the digits 0 & 1 in column 2 and get 1.

Step 3: We'll start by adding the digits 2 & 5 in column 3 and get 7.

So, 204 + 515 = 719.

