15% off $75 = $63.75. You save $11.25.
Equation: $75 − (15% × $75) = $75 − $11.25 = $63.75.
Another way to read it: you pay 85% of the original price — that's $63.75.
$63.75. The discount is $11.25 and the final price you pay is $63.75.
You pay $63.75 (before tax). That's $75 minus a $11.25 discount.