Okay, we are tasked with adding 8815 and 1515. Let's begin!

Step 1: We'll start by adding the digits 5 & 5 in column 1 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 1 & 1 in column 2 and get 3.

Step 3: We'll start by adding the digits 8 & 5 in column 3 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 8 & 1 in column 4 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

So, 8815 + 1515 = 10330.

