OK, let's do this. We've got 1305 and 1203 and we're adding them all together.

Step 1: We'll start by adding the digits 5 & 3 in column 1 and get 8.

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 1 & 1 in column 4 and get 2.

So, 1305 + 1203 = 2508.

