We've got two numbers: 3609 and 1329. Let's find their sum.

Step 1: We'll start by adding the digits 9 & 9 in column 1 and get 18.
We'll write down the last digit 8 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 0 & 2 in column 2 and get 3.

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

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

So, 3609 + 1329 = 4938.

