Let's get this math done. We have 306 and 8423 and we're going to add them all together.

Step 1: We'll start by adding the digits 6 & 3 in column 1 and get 9.

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

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

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

So, 306 + 8423 = 8729.

