The local bookstore is having a sole on used books . nate bought 3 hardcover books and 7 paperback books and spent 29.50. tia bought 2 hardcover books and 5 paperback books and spent 20.50. what is the cost of a hardcover book

The first thing we must do for this case is to define variables.
 We have then:
 x = cost of a hardcover book
 y = cost of a paperback book
 We write the system of equations:
 3x + 7y = 29.50
 2x + 5y = 20.50
 The solution to the system is:
 x = 4 $
 y = 2.5 $
 
 the cost of a hardcover book is $ 4