10% off $50 = $45. You save $5.
Equation: $50 − (10% × $50) = $50 − $5 = $45.
Another way to read it: you pay 90% of the original price — that's $45.
$45. The discount is $5 and the final price you pay is $45.
You pay $45 (before tax). That's $50 minus a $5 discount.