Question

Uncle Ian spent $59 at a book store. He bought science fiction and mystery novels. The science fiction novels cost $7 apiece and the mystery novels cost $9 apiece. If uncle Ian bought 7 novels, how many of each type did he buy?

Answer 1

2 science fiction and 5 mystery

Explanation:

First, we will set up a system of equations.

x (science fiction) y (mystery)

x + y = 7 This is the total books bought.

7x + 9y = 59 The amount of each set to the total cost.

Now we solve.

(-7)x + y = 7 equals

-7x - 7y = -49

added to

7x + 9y = 59

this equals

2y = 10

y = 5

Now we know one. We can plug it in to find the other value.

x + 5 = 7

x = 2