After a 20% discount, the price of a pair of shoes is 250 yuan, which is much cheaper than the original one.
一双鞋子打八折后价格为250元，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">250 / (4/5)</gadget>
<output>625/2 = around 312.5</output>

<gadget id="calculator">(625/2) - 250</gadget>
<output>125/2 = around 62.5</output>

<result>125/2 = around 62.5</result>