What is the original price of a drum set if the sale price is 1099 and it was discounted at 10 percent?

10% means 10/100 = 0.1

But, you are " paying forward, " so to speak, so use the inverse of 10% and divide the sale price by 90% = 0.9.

$1099/0.9

= $1221.11

===============original price of drum set