Answer:
The book was $12 after the 20% discount
Step-by-step explanation:
Recall that 20% corresponds to the decimal fraction 0.20.
Thus, the price of the book after discount is found by multiplying $15 by
1.00 - 0.20, or 0.80:
0.80($15) = $12
The book was $12 after the 20% discount.
