Xiao Ming bought 3 fairy tale books, paid 20 yuan, and got back 0.8 yuan. How much is the average price of each fairy tale book?
小明买3本童话书，付出20元，找回0.8元．平均每本童话书多少元？
<gadget id="calculator">20 - 0.8</gadget>
<output>19.2</output>

<gadget id="calculator">19.2 / 3</gadget>
<output>6.4</output>

<result>6.4</result>