Question

Alana and Petra go to a used book sale, where every book is the same price. Alana buys 5 books and Petra buys 4 books. They run into their friend Angus,who really loves to read, and discover that he has bought 19 books. Angus received a $10 discount, but he still spent $5 more than Alana and Petra combined. How much does one book cost?

Answer 1

Alana and Petra bought 9 books combined.
Angus bought 19 books and had a $10 discount.
Angus spent $5 more than Alana and Petra combined.

This means that the price of 19 books is $15 more than the price of 9 books. 19 books is 10 books more than 9 books.

Giving you 10 books = $15, 1 book = $1.50