Qisi brought 50 yuan, spent 15.8 yuan on stationery, and 24.2 yuan on toys. How much money does he have left?
奇思带50元钱，买文具花了15.8元，买玩具花了24.2元．他还剩多少元？
<gadget id="calculator">15.8 + 24.2</gadget>
<output>40</output>

<gadget id="calculator">50 - 40</gadget>
<output>10</output>

<result>10</result>