Not to worry, we've got 8744 and 7921. Let's get to adding them!

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

Step 2: We'll start by adding the digits 4 & 2 in column 2 and get 6.

Step 3: We'll start by adding the digits 7 & 9 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 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, 8744 + 7921 = 16665.

