Let's solve this addition problem. We have 4320 and 4609, and we need to add them 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 2 & 0 in column 2 and get 2.

Step 3: We'll start by adding the digits 3 & 6 in column 3 and get 9.

Step 4: We'll start by adding the digits 4 & 4 in column 4 and get 8.

So, 4320 + 4609 = 8929.

