The original price of a piece of clothing is 500 yuan, how much is the price after a 20% discount?
一件衣服原件是500元，打八折后售价是多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">500 * (4/5)</gadget>
<output>400</output>

<result>400</result>