25% off $50 = $37.50. You save $12.50.
Equation: $50 − (25% × $50) = $50 − $12.50 = $37.50.
Another way to read it: you pay 75% of the original price — that's $37.50.
$37.50. The discount is $12.50 and the final price you pay is $37.50.
You pay $37.50 (before tax). That's $50 minus a $12.50 discount.