Not to worry, we've got 8240 and 439. Let's get to adding them!

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 4 & 3 in column 2 and get 7.

Step 3: We'll start by adding the digits 2 & 4 in column 3 and get 6.

Step 4: We'll start by adding the digits 8 & 0 in column 4 and get 8.

So, 8240 + 439 = 8679.

