Mom spent 400 yuan to buy a dress with a 20% discount. How much is the original price of this dress?
妈妈花了400元买了一件打八折的衣服，这件衣服原价多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

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

<result>500</result>