Xiao Ming's mother bought mangoes for 25.50 yuan and watermelons for 16.80 yuan in the fruit supermarket. She gave the cashier 50 yuan. How much should she get back?
小明的妈妈在水果超市买了25.50元的芒果，16.80元的西瓜，她给收银员50元，应找回多少元？
<gadget id="calculator">25.5 + 16.8</gadget>
<output>42.3</output>

<gadget id="calculator">50 - 42.3</gadget>
<output>7.7</output>

<result>7.7</result>