Question

ABC bookstore sells one customer 12 used books and 4 new books for $120. Another customer buys 14 used books and 2 new books for $100. How much is one used book (u), and one new book (n)?​

Answer 1

$5 per used book, $15 per new book

Explanation:

Let u = cost of one used book and

n = cost of one new book.

12u + 4n = 120-------->3u + n = 30

14u + 2n = 100-------->7u + n = 50

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4u = 20

u = 5, n = 15

So one used book costs $5, and one new book costs $15.