Commodities with an original price of 80 yuan are sold at a 25% discount, which is how much cheaper than the original price.
原价80元的商品打七五折出售，比原价便宜多少元．
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">80 * (1/4)</gadget>
<output>20</output>

<result>20</result>