Wang Jun buys a pen for 5 yuan and a notebook for 2 yuan, pays the salesperson 10 yuan, and asks how much to get back. what is the incorrect formula
王军买一枝5元的钢笔和一本2元的笔记本，付给售货员10元钱，求应找回多少元．不正确的算式是多少
<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<gadget id="calculator">10 - 3</gadget>
<output>7</output>

<result>7</result>