Ben and Michael went to buy stereo systems at a sale. The usual price of 1 stereo system was $1800 each.

SALE
Buy 1 stereo system at 15% discount
Buy 2 or more stereo systems at 25% discount each

1. Ben bought 1 stereo system. How much did he pay?
2. What is the maximum number of stereo systems Michael can buy if he has $7000?

(a)
Discounted price of 1 stereo system in percent if only 1 was bought
= 100% - 15%
= 85%

100% of 1 stereo system = 1800
1% of 1 stereo system = 1800 ÷ 100 = 18
85% of 1 stereo system = 85 x 18 = 1530 

Amount that Ben paid for 1 stereo system = $1530

(b)
Discounted price of 1 stereo system in percent if more than 1 was bought
= 100% - 25%
= 75%

75% of 1 stereo system = 75 x 18 = 1350

Amount that Michael paid for 1 stereo system = $1350

Maximum number of stereo systems that Michael can buy if he has $7000
= 7000 ÷ 1350
= 5 r 250

Answer(s): (a) $1530; (b) 5