Answer:
You need to buy 12 books to get a $15 coupon.
Explanation:
Giving the following information:
You get a $5 coupon for every 4 books you buy.
First, we need to structure the total coupon formula:
Total coupon= 5*x
x= pack of four books
Now, for $15
15 = 5x
15/5= x
3= x
4*3= 12
You need to buy 12 books to get a $15 coupon.