Let's get this math done. We have 8931 and 7993 and we're going to add them all together.

Step 1: We'll start by adding the digits 1 & 3 in column 1 and get 4.

Step 2: We'll start by adding the digits 3 & 9 in column 2 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 9 & 9 in column 3 and get 19.
We'll write down the last digit 9 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 8 & 7 in column 4 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

So, 8931 + 7993 = 16924.

