Mom went to the store and bought a pen for 8.4 yuan and a pair of badminton rackets for 69.8 yuan. She paid the salesperson 100 yuan. How much should she get back?
妈妈到商店买了一支钢笔8.4元，买一副羽毛球拍69.8元，她付给售货员100元，应找回多少钱？
<gadget id="calculator">100 - 8.4 - 69.8</gadget>
<output>21.8</output>

<result>21.8</result>