Xiaohua bought 5 books, paid a total of 30 yuan, and got back 2.5 yuan. How much is each book?
小华买了5本书，一共付了30元，找回2.5元，每本书多少元？
<gadget id="calculator">30 - 2.5</gadget>
<output>27.5</output>

<gadget id="calculator">27.5 / 5</gadget>
<output>5.5</output>

<result>5.5</result>