Okay, we are tasked with adding 28 and 9909. Let's begin!

Step 1: We'll start by adding the digits 8 & 9 in column 1 and get 17.
We'll write down the last digit 7 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 2 & 0 in column 2 and get 3.

Step 3: We'll start by adding the digits 0 & 9 in column 3 and get 9.

Step 4: We'll start by adding the digits 0 & 9 in column 4 and get 9.

So, 28 + 9909 = 9937.

