We've got two numbers: 4006 and 9321. Let's find their sum.

Step 1: We'll start by adding the digits 6 & 1 in column 1 and get 7.

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

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

Step 4: We'll start by adding the digits 4 & 9 in column 4 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 4006 + 9321 = 13327.

