On Children's Day, bookstores sell children's books at a 20% discount. Xiao Ming bought a book with 7.20 yuan, how much is the original price of this book?
六一儿童节，书店降价20%出售儿童读物．小明用7.20元钱买了一本书，这本书的原价是多少元？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">7.2 / (4/5)</gadget>
<output>9</output>

<result>9</result>