Here is an example of something I had thats similar to yours:
Max wants to buy a couch at The Furniture Store. The couch he is considering had been marked on sale for 20% off and was selling for $320. The day he comes in to buy the couch, it has been marked down an additional 40% off of the sale price. What is the difference in the original price of the couch and what Max paid for the couch?
(320) / (0.8) = 400. The couch has been marked down an additional 40% from the sale price of $320. $320 * 0.6 = $192. $400 – $192 = $208.