Okay, we are tasked with adding 758 and 821. Let's begin!

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

Step 2: We'll start by adding the digits 5 & 2 in column 2 and get 7.

Step 3: We'll start by adding the digits 7 & 8 in column 3 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

So, 758 + 821 = 1579.

