Congcong goes to the stationery store, and it costs 16.8 yuan to buy colored pens, and 25.7 yuan to buy a writing board. He pays the salesperson 50 yuan, how much should he get back?
聪聪去文具商店，买彩笔需要16.8元，买写字板需要25.7元，他付给售货员50元，应找回多少元？
<gadget id="calculator">50 - 16.8 - 25.7</gadget>
<output>7.5</output>

<result>7.5</result>