Let's get this math done. We have 6815 and 8813 and we're going to add them all together.

Step 1: We'll start by adding the digits 5 & 3 in column 1 and get 8.

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

Step 3: We'll start by adding the digits 8 & 8 in column 3 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 6 & 8 in column 4 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

So, 6815 + 8813 = 15628.

