What is the equation to solve this problem?

Question

A tape costs $4 less than a CD. Oshkosh bought one CD and five tapes. If the total cost was $70, what was the price of the CD?

Answer 1

The unknown quantities are the unit cost of a tape and of a CD. Let x = the cost of a CD. Then (x - 4) is the cost of a tape. The total cost of the purchase is 70 dollars. Since there was one CD and five tapes involved in the purchase, the total cost can be written algebraically as:

 

x + 5(x - 4) = 70 

 

Can you solve this problem for x, Lola?