Aunt Zhang bought a set of "Andersen's Fairy Tales", a total of 3 volumes. She paid 50 yuan and got 2.6 yuan back. How much is the average book?
张阿姨买了一套《安徒生童话》集，共3本，付了50元，找回2.6元钱．平均每本书多少钱？
<gadget id="calculator">50 - 2.6</gadget>
<output>47.4</output>

<gadget id="calculator">47.4 / 3</gadget>
<output>15.8</output>

<result>15.8</result>