word problem, need solution

Question

A stamp collection consists of 5 cent 13 cent and 18 cent stamps. The number of 13 cent stamps is one less than twice the number of 5 cent stamps. The number of 18 cent stamps is five more than the number of 13 cent stamps. The total value of all the stamps is $2.60. Find the number of 13 cent stamps in the collection

Answer 1

x = # of 5 cent stamps

y= # of 13 cent tamps

z = # of 18 cent stamps

y=2x-1

z= y+5 = 2x-1+5 = 2x+4

Value of stamps:

5x+13y+18z = 260 ( I wrote everything in cents)

5x+13(2x-1) +18(2x+4) =260

5x+26x-13+36x+72 =260

67x+59 =260

67x = 260-59

67x = 201

x = 201/67 = 3

so, number of 13 cent stamps = y=2x-1=2(3)-1 =5