50% off $200 = $100. You save $100.
Equation: $200 − (50% × $200) = $200 − $100 = $100.
Another way to read it: you pay 50% of the original price — that's $100.
$100. The discount is $100 and the final price you pay is $100.
You pay $100 (before tax). That's $200 minus a $100 discount.