50% off $75 = $37.50. You save $37.50.
Equation: $75 − (50% × $75) = $75 − $37.50 = $37.50.
Another way to read it: you pay 50% of the original price — that's $37.50.
$37.50. The discount is $37.50 and the final price you pay is $37.50.
You pay $37.50 (before tax). That's $75 minus a $37.50 discount.