The original price of a coat is 500 yuan. It is now on sale with a 20% discount. How much is this coat cheaper than before?
一件上衣原价500元．现在打八折销售，这件上衣比原来便宜了多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">500 * (1/5)</gadget>
<output>100</output>

<result>100</result>