Xiao Ming buys 5 books of the same price, pays the salesperson 20 yuan, and gets back 0.5 yuan. How much is the price of each book?
小明买5本同样价格的本子，付给营业员20元，找回0.5元．每本本子的价格是多少元？
<gadget id="calculator">20 - 0.5</gadget>
<output>19.5</output>

<gadget id="calculator">19.5 / 5</gadget>
<output>3.9</output>

<result>3.9</result>