OK, let's do this. We've got 3300 and 6215 and we're adding them all together.

Step 1: We'll start by adding the digits 0 & 5 in column 1 and get 5.

Step 2: We'll start by adding the digits 0 & 1 in column 2 and get 1.

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

Step 4: We'll start by adding the digits 3 & 6 in column 4 and get 9.

So, 3300 + 6215 = 9515.

