Not to worry, we've got 6640 and 5290. Let's get to adding them!

Step 1: We'll start by adding the digits 0 & 0 in column 1 and get 0.

Step 2: We'll start by adding the digits 4 & 9 in column 2 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 6 & 2 in column 3 and get 9.

Step 4: We'll start by adding the digits 6 & 5 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 6640 + 5290 = 11930.

