We've got two numbers: 511 and 320. Let's find their sum.

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

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

Step 3: We'll start by adding the digits 5 & 3 in column 3 and get 8.

So, 511 + 320 = 831.

