A piece of clothing is 320 yuan after a 20% discount. How much is this piece of clothing cheaper?
一件衣服打八折后是320元，这件衣服便宜了多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">320 / (4/5)</gadget>
<output>400</output>

<gadget id="calculator">400 - 320</gadget>
<output>80</output>

<result>80</result>