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)
![1.50(25-p) + 0.50 p = 26.50](https://tex.z-dn.net/?f=1.50%2825-p%29%20%2B%200.50%20p%20%3D%2026.50)
![37.5-1.50p + 0.50 p = 26.50](https://tex.z-dn.net/?f=37.5-1.50p%20%2B%200.50%20p%20%3D%2026.50)
![p = 11](https://tex.z-dn.net/?f=p%20%3D%2011)
Substitute back in equation (1),
![h+11= 25](https://tex.z-dn.net/?f=h%2B11%3D%2025)
![h=14](https://tex.z-dn.net/?f=h%3D14)
i.e. there are 11 paperback books and 14 hardcover books.
Therefore, Number of books did Gillian buy is 11.