Cody and Justin went to buy stereo systems at a sale. The usual price of 1 stereo system was $400 each.

SALE
Buy 1 stereo system at 20% discount
Buy 2 or more stereo systems at 35% discount each

1. Cody bought 1 stereo system. How much did he pay?
2. What is the maximum number of stereo systems Justin can buy if he has $6000?

(a)
Discounted price of 1 stereo system in percent if only 1 was bought
= 100% - 20%
= 80%

100% of 1 stereo system = 400
1% of 1 stereo system = 400 ÷ 100 = 4
80% of 1 stereo system = 80 x 4 = 320 

Amount that Cody paid for 1 stereo system = $320

(b)
Discounted price of 1 stereo system in percent if more than 1 was bought
= 100% - 35%
= 65%

65% of 1 stereo system = 65 x 4 = 260

Amount that Justin paid for 1 stereo system = $260

Maximum number of stereo systems that Justin can buy if he has $6000
= 6000 ÷ 260
= 23 r 20

Answer(s): (a) $320; (b) 23