After a 20% discount, the price of a piece of clothing is 200 yuan, which is how much cheaper than the original price.
一件衣服打八折后售价是200元，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">200 / (4/5)</gadget>
<output>250</output>

<gadget id="calculator">250 - 200</gadget>
<output>50</output>

<result>50</result>