Cd's were purchased for $60 per dozen and sold at $35 per four cd's. find the profit on 8 dozen cd's.

They bought cds at $60 per dozen. They sold four of those cd's for 35. since every cd is $5 (60/12=5), then they bought 4 cd's for $20. so since they sold 4 at $35, you subtract 35 and 20

35 - 20=15. 15 is the answer