Let's break this down. We're going to add 1284 and 1185 together.

Step 1: We'll start by adding the digits 4 & 5 in column 1 and get 9.

Step 2: We'll start by adding the digits 8 & 8 in column 2 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 2 & 1 in column 3 and get 4.

Step 4: We'll start by adding the digits 1 & 1 in column 4 and get 2.

So, 1284 + 1185 = 2469.

