A shopping mall is carrying out book promotion activities, and a book is 7.8 yuan cheaper than the original price after a 15% discount. How much is the original price of this book?
某商场进行图书促销活动，一本书打完折九五折后比原价便宜了7.8元，这本书原价多少元？
<gadget id="calculator">95 / 100</gadget>
<output>19/20 = around 0.95</output>

<gadget id="calculator">1 - (19/20)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">7.8 / (1/20)</gadget>
<output>156</output>

<result>156</result>