The extra-curricular reading materials in Xinhua Bookstore can be discounted by 20% with the discount card. Xiaohua bought a set of books with the discount card and saved 7.2 yuan. What is the original price of this set of books?
新华书店的课外读物书凭优惠卡可打八折，小华用优惠卡买了一套书，省了7.2元，这套书的原价是多少元．
<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">7.2 / (1/5)</gadget>
<output>36</output>

<result>36</result>