30% off $150 = $105. You save $45.
Equation: $150 − (30% × $150) = $150 − $45 = $105.
Another way to read it: you pay 70% of the original price — that's $105.
$105. The discount is $45 and the final price you pay is $105.
You pay $105 (before tax). That's $150 minus a $45 discount.