Xiao Ming buys a pencil for 80 cents, and buys an eraser for 50 cents. He paid the salesperson 2 yuan. How much should I get back?
小明买一枝铅笔用去8角钱，买一块橡皮用去5角．他付给营业员2元钱．应找回多少钱？
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">20 - 8 - 5</gadget>
<output>7</output>

<result>7</result>