20% off $75 = $60. You save $15.
Equation: $75 − (20% × $75) = $75 − $15 = $60.
Another way to read it: you pay 80% of the original price — that's $60.
$60. The discount is $15 and the final price you pay is $60.
You pay $60 (before tax). That's $75 minus a $15 discount.