Let's break this down. We're going to add 9306 and 8621 together.

Step 1: We'll start by adding the digits 6 & 1 in column 1 and get 7.

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

Step 3: We'll start by adding the digits 3 & 6 in column 3 and get 9.

Step 4: We'll start by adding the digits 9 & 8 in column 4 and get 17.
We'll write down the last digit 7 and carry the 1 to the next column.

So, 9306 + 8621 = 17927.

