We've got two numbers: 120 and 721. Let's find their sum.

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 2 & 2 in column 2 and get 4.

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

So, 120 + 721 = 841.

