Here we go! We're going to add 1540 and 9909 together.

Step 1: We'll start by adding the digits 0 & 9 in column 1 and get 9.

Step 2: We'll start by adding the digits 4 & 0 in column 2 and get 4.

Step 3: We'll start by adding the digits 5 & 9 in column 3 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 1 & 9 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 1540 + 9909 = 11449.

