a park purchased equipment from a manufacturer for a list price of $42,000 minus trade discounts of 30/20/15. How do you calculate the amount of the trade discount on the purchase?

So they pay .7(.8)(.85) or .476 of the original price

or they paid .476(42000) = 19,992

discount = 42000-19992 = 22008

discount rate = 22008/42000 = .524 or 52.6%