A piece of clothing is sold at a 10% discount, and the current price is 180 yuan, how much has it been reduced.
一件衣服打九折出售，现在售价是180元，降低了多少元．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">180 / (9/10)</gadget>
<output>200</output>

<gadget id="calculator">200 - 180</gadget>
<output>20</output>

<result>20</result>