Here we go! We're going to add 9481 and 9900 together.

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

Step 2: We'll start by adding the digits 8 & 0 in column 2 and get 8.

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

Step 4: We'll start by adding the digits 9 & 9 in column 4 and get 19.
We'll write down the last digit 9 and carry the 1 to the next column.

So, 9481 + 9900 = 19381.

