10% off $25 = $22.50. You save $2.50.
Equation: $25 − (10% × $25) = $25 − $2.50 = $22.50.
Another way to read it: you pay 90% of the original price — that's $22.50.
$22.50. The discount is $2.50 and the final price you pay is $22.50.
You pay $22.50 (before tax). That's $25 minus a $2.50 discount.