Okay, we are tasked with adding 664 and 422. Let's begin!

Step 1: We'll start by adding the digits 4 & 2 in column 1 and get 6.

Step 2: We'll start by adding the digits 6 & 2 in column 2 and get 8.

Step 3: We'll start by adding the digits 6 & 4 in column 3 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

So, 664 + 422 = 1086.

