Answer: She bought 17 books
Explanation:
Add $6 to the amount that she paid to find out how much money she would have paid.
45 + 6 = 51 so she would have paid $51
Now divide 51 by 3 to find out how many books she bought.
51 / 3 = 17
So because of the discount, she paid $45 for 17 books.