Xiaopang bought 3 books, the prices are 13.7 yuan, 7.3 yuan and 12.64 yuan respectively. If he paid 50 yuan, how much should he get back?
小胖买了3本书，价格分别是13.7元、7.3元和12.64元，付出50元，应找回多少元？
<gadget id="calculator">13.7 + 7.3 + 12.64</gadget>
<output>33.64</output>

<gadget id="calculator">50 - 33.64</gadget>
<output>16.36</output>

<result>16.36</result>