The price of a book is 20 yuan, and now the price is reduced by 15%, what is the current price?
一本书的定价是20元，现在降价15%出售，现价是多少元．
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 - (3/20)</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">20 * (17/20)</gadget>
<output>17</output>

<result>17</result>