Let's break this down. We're going to add 6404 and 8247 together.

Step 1: We'll start by adding the digits 4 & 7 in column 1 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 0 & 4 in column 2 and get 5.

Step 3: We'll start by adding the digits 4 & 2 in column 3 and get 6.

Step 4: We'll start by adding the digits 6 & 8 in column 4 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

So, 6404 + 8247 = 14651.

