Write a system of equations to model this situation. Then use your system to solve. At a garage sale a CD costs three books and 2 CDs. You spent $18. What is the price of a CD and the price of a book?
If questions is rewritten saying a CD cost is 3 books. and on 3 books and 2 CD you spent $18. Then we can solve the problem as below.
b = price of books & c= price of cds
3b + 2c = 18
c = 3b
I am using substitution to solve
3b + 2(3b) = 18 I solved for one variable
3b +6b = 18
9b = 18
b = $2 Cost of the book
c = $6 Cost of the CD