Xiaohua bought two story books, one cost 19.8 yuan and the other cost 23.4 yuan. She paid the salesperson 50 yuan. How much should she get back?
小华买了两本故事书，一本花了19.8元，另一本花了23.4元，她付给售货员50元，应找回多少钱？
<gadget id="calculator">19.8 + 23.4</gadget>
<output>43.2</output>

<gadget id="calculator">50 - 43.2</gadget>
<output>6.8</output>

<result>6.8</result>