Let's break this down. We're going to add 6700 and 3131 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 0 & 3 in column 2 and get 3.

Step 3: We'll start by adding the digits 7 & 1 in column 3 and get 8.

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

So, 6700 + 3131 = 9831.

