Teacher Li sold 8 copies of the same book, paid the cashier 100 yuan, and got back 22.4 yuan. How much is each book?
李老师卖了8本同样的书，付给收银员100元，找回了22.4元，每本书多少元？
<gadget id="calculator">100 - 22.4</gadget>
<output>77.6</output>

<gadget id="calculator">77.6 / 8</gadget>
<output>9.7</output>

<result>9.7</result>