75% off $100 = $25. You save $75.
Equation: $100 − (75% × $100) = $100 − $75 = $25.
Another way to read it: you pay 25% of the original price — that's $25.
$25. The discount is $75 and the final price you pay is $25.
You pay $25 (before tax). That's $100 minus a $75 discount.