OK, let's do this. We've got 2300 and 1200 and we're adding them all together.

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

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

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 2 & 1 in column 4 and get 3.

So, 2300 + 1200 = 3500.

