Let's break this down. We're going to add 4430 and 2509 together.

Step 1: We'll start by adding the digits 0 & 9 in column 1 and get 9.

Step 2: We'll start by adding the digits 3 & 0 in column 2 and get 3.

Step 3: We'll start by adding the digits 4 & 5 in column 3 and get 9.

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

So, 4430 + 2509 = 6939.

