Let's solve this addition problem. We have 303 and 393, and we need to add them together.

Step 1: We'll start by adding the digits 3 & 3 in column 1 and get 6.

Step 2: We'll start by adding the digits 0 & 9 in column 2 and get 9.

Step 3: We'll start by adding the digits 3 & 3 in column 3 and get 6.

So, 303 + 393 = 696.

