Answer:
$40
Explanation:
Original price - discount = sales price
discount = original price * percent off
Substituting this in
Original price - original price * percent off = sales price
Factor out the original price
Original price (1-percent off) = sales price
We know the sales price = 36
and we know the percent off = 10 percent = .1
Substituting in
Original price (1-.1) = 36
Original price (.9) = 36
Divide both sides by .9
Original price *.9/.9 = 36/.9
Original price = 40