We have numbers 6621 and 3116. Let's start adding them together.

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

Step 2: We'll start by adding the digits 2 & 1 in column 2 and get 3.

Step 3: We'll start by adding the digits 6 & 1 in column 3 and get 7.

Step 4: We'll start by adding the digits 6 & 3 in column 4 and get 9.

So, 6621 + 3116 = 9737.

