How do i figure out how many of each type of jeans were sold?

Question

Banana Republic at the Orlando, Florida, outlet store sells casual jeans for $40 and dress jeans for $60. If customers bought 5 times more casual than dress jeans and last month’s sales totaled $6,500, how many of each type of jeans were sold?

Answer 1

40C+60D =6500

4C +6D = 650

C=5D

4(5D) + 6D = 650

20D + 6D = 650

26D = 650

D = 650/26 = 25 dress jeans

C=5D = 125 casual jeans