Let's break this down. We're going to add 439 and 313 together.

Step 1: We'll start by adding the digits 9 & 3 in column 1 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 3 & 1 in column 2 and get 5.

Step 3: We'll start by adding the digits 4 & 3 in column 3 and get 7.

So, 439 + 313 = 752.

