Answer:
Number of books did Gillian buy is 11.
Step-by-step explanation:
Given : Gillian purchased 25 books at the library book sale. Each hardcover book cost $1.50, and each paperback book cost $0.50. Gillian spent a total of $26.50.
To find : How many paperback books did Gillian buy?
Solution :
The book costs can be represented by the system of equations below.
......(1)
......(2)
Solving the system of equations by substitution method
Substitute h=25-p from (1) into (2)



Substitute back in equation (1),


i.e. there are 11 paperback books and 14 hardcover books.
Therefore, Number of books did Gillian buy is 11.