The current price of a shirt is 72 yuan, which is 20% lower than the original price. How much is the reduction?
一件衬衫现价72元，比原价降低20%，降低了多少元．
<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">72 / (4/5)</gadget>
<output>90</output>

<gadget id="calculator">90 * (1/5)</gadget>
<output>18</output>

<result>18</result>