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