Okay, we are tasked with adding 1720 and 1. Let's begin!

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 & 0 in column 2 and get 2.

Step 3: We'll start by adding the digits 7 & 0 in column 3 and get 7.

Step 4: We'll start by adding the digits 1 & 0 in column 4 and get 1.

So, 1720 + 1 = 1721.

