The original price of a commodity is 450 yuan. After the 20% discount, how much is it cheaper than the original price?
一种商品原来售价450元，打八折后，比原价便宜了多少元？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">450 * (4/5)</gadget>
<output>360</output>

<gadget id="calculator">450 - 360</gadget>
<output>90</output>

<result>90</result>