Xiaohong, Xiaoli, and Xiaomin each have several calendar cards. If Xiaohong gives Xiaoli 13, Xiaoli gives Xiaomin 23, and Xiaomin gives Xiaohong 3, then they each have 40. It turns out how many calendar cards Xiao Min has.
小红、小丽、小敏三人各有年历卡若干张．如果小红给小丽13张，小丽给小敏23张，小敏给小红3张，那么她们每人各有40张．原来小敏有年历卡多少张．
<gadget id="calculator">3 - 23</gadget>
<output>-20</output>

<gadget id="calculator">40 + (-20)</gadget>
<output>20</output>

<result>20</result>