There are 16 children playing games, 3 children joined in later, and 6 children went home, how many children are playing now?
有16位小朋友在玩游戏，后来有3位小朋友加入，又有6位小朋友回家去了，现在有多少位小朋友在玩．
<gadget id="calculator">3 - 6</gadget>
<output>-3</output>

<gadget id="calculator">16 + (-3)</gadget>
<output>13</output>

<result>13</result>