Okay, we are tasked with adding 100 and 2089. Let's begin!

Step 1: We'll start by adding the digits 0 & 9 in column 1 and get 9.

Step 2: We'll start by adding the digits 0 & 8 in column 2 and get 8.

Step 3: We'll start by adding the digits 1 & 0 in column 3 and get 1.

Step 4: We'll start by adding the digits 0 & 2 in column 4 and get 2.

So, 100 + 2089 = 2189.

