Okay, we are tasked with adding 1209 and 2452. Let's begin!

Step 1: We'll start by adding the digits 9 & 2 in column 1 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 0 & 5 in column 2 and get 6.

Step 3: We'll start by adding the digits 2 & 4 in column 3 and get 6.

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

So, 1209 + 2452 = 3661.

