Let's break this down. We're going to add 6646 and 33 together.

Step 1: We'll start by adding the digits 6 & 3 in column 1 and get 9.

Step 2: We'll start by adding the digits 4 & 3 in column 2 and get 7.

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 6 & 0 in column 4 and get 6.

So, 6646 + 33 = 6679.

