Question

A bookstore sold 50 hardcover paperback books for a total of $600. If a hardcover book costs $20 and a paperback book costs $10, how many hardcover books were sold?​

Answer 1

Let h = hardcover and p=paperback

Set up the following equations

h + p = 50
20h + 10p = 600

Then use the first equation to solve for p
p=50-h

Now substitute into the second equation
20h + 10(50-h) = 600
20h + 500 - 10h = 600
10h = 100
h = 10

10 hardcover books were sold