Tommy and Rael went to buy stereo systems at a sale. The usual price of 1 stereo system was $200 each.

SALE
Buy 1 stereo system at 15% discount
Buy 2 or more stereo systems at 30% discount each

1. Tommy bought 1 stereo system. How much did he pay?
2. What is the maximum number of stereo systems Rael can buy if he has $3000?

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

100% of 1 stereo system = 200
1% of 1 stereo system = 200 ÷ 100 = 2
85% of 1 stereo system = 85 x 2 = 170 

Amount that Tommy paid for 1 stereo system = $170

(b)
Discounted price of 1 stereo system in percent if more than 1 was bought
= 100% - 30%
= 70%

70% of 1 stereo system = 70 x 2 = 140

Amount that Rael paid for 1 stereo system = $140

Maximum number of stereo systems that Rael can buy if he has $3000
= 3000 ÷ 140
= 21 r 60

Answer(s): (a) $170; (b) 21