Liu Ming needs 15.8 yuan to buy pens and 27.9 yuan to buy books. He gives 50 yuan to the salesperson. How much should he get back?
刘明买钢笔需要15.8元，买书需要27.9元，他给售货员50元，应找回多少元？
<gadget id="calculator">15.8 + 27.9</gadget>
<output>43.7</output>

<gadget id="calculator">50 - 43.7</gadget>
<output>6.3</output>

<result>6.3</result>