What's the price and how much is off?
Multiply the original price by the fraction left after the discount:
The discount amount is the original price times the discount percent:
Most stores discount the pre-tax price, then add sales tax on the reduced amount:
Is a 50% discount the same as buying at half price? Yes — the sale price is exactly half the original.
Is tax added to the original or the discounted price? Usually the discounted price, which means you pay less tax too.