After the price of a piece of clothing is reduced by 20%, the price is 80 yuan. How much is the original price of this dress?
一件衣服降价二折后，售价为80元．这件衣服原价多少元？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">80 / (4/5)</gadget>
<output>100</output>

<result>100</result>