math
posted by Amanda .
An amusement park purchased equipment from a manufacturer for a list price of
$42,000, minus trade discounts of 30/20/15. Calculate the amount of the trade discount
on the purchase.
A. $19,992 C. $23,520
B. $22,008 D. $29,400
could someone help me understand how to solve this problem

after the first discount of 30% you will have 70% left to pay, or 42000(.7)
then after another discount of 20% you will have to pay 80% or the above or
42000(.7)(.8)
and finally after another 15% you have to pay 85% of the above or
42000(.7)(.8)(.85) = 19992 
I just read the question again.
the answer I left you with would be the final cost, but it asked for the discount
so the discount would be
42000  19992 = 22008 or (B)