We have numbers 4415 and 9721. Let's start adding them together.

Step 1: We'll start by adding the digits 5 & 1 in column 1 and get 6.

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 4 & 7 in column 3 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 4 & 9 in column 4 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

So, 4415 + 9721 = 14136.

