Here we go! We're going to add 3660 and 8021 together.

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

Step 2: We'll start by adding the digits 6 & 2 in column 2 and get 8.

Step 3: We'll start by adding the digits 6 & 0 in column 3 and get 6.

Step 4: We'll start by adding the digits 3 & 8 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 3660 + 8021 = 11681.

