Bookstore promotion, all books are 20% off sales. Jiajia bought a copy of "Fairy Tales", which cost 4.5 yuan less. How much is the original price of this book?
书店促销，所有图书一律八折销售．佳佳买了一本《童话故事》，少花了4.5元．这本书的原价的多少元？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">4.5 / (1/5)</gadget>
<output>22.5</output>

<result>22.5</result>