A book is sold at a 15% discount, which is 3 yuan cheaper than the original price. What is the original price of this book?
一本书按八五折出售比原价便宜了3元，这本书的原价是多少元．
<gadget id="calculator">85 / 100</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">1 - (17/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">3 / (3/20)</gadget>
<output>20</output>

<result>20</result>