Calculate percentage of X, quick & simple.
Let's take a quick example here:
You have a Target coupon of $640 and you need to know how much will you save on your purchase if the discount is 90 percent.
Solution:
Amount Saved = Original Price x Discount in Percent / 100
Amount Saved = (640 x 90) / 100
Amount Saved = 57600 / 100
Amount Saved = $576 (answer).
In other words, a 90% discount for a purchase with an original price of $640 equals $576 (Amount Saved), so you'll end up paying 64.