jacket is held on Double 11. The price is 180 yuan after a discount (1/10) from the original price. How much is the discount?
一件上衣双11搞活动，比原价优惠(1/10)后售价180元，优惠多少元？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</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>