Okay, we are tasked with adding 8216 and 1421. Let's begin!

Step 1: We'll start by adding the digits 6 & 1 in column 1 and get 7.

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 2 & 4 in column 3 and get 6.

Step 4: We'll start by adding the digits 8 & 1 in column 4 and get 9.

So, 8216 + 1421 = 9637.

