Question

Alana and Petra go to a used book sale, where every book is the same price. Alana buys 4
books and Petra buys 2
books. They run into their friend Angus, who really loves to read, and discover that he has bought 16
books. Angus received a 15
discount, but he still spent 5
more than Alana and Petra combined. How much does one book cost?

Answer 1

Let the price per book be p (dollars). Angus paid 16p − 15, and Alana and Petra together paid 4p + 2p = 6p. Angus paid $5 more than they did, so

16p − 15 = 6p + 5
10p = 20
p = 2.

One book costs $2.