Among the 30 students, 8 can speak French, 16 can speak English, 3 can neither speak French nor English, how many students can speak two languages.
30名学生中，8人会说法语，16人会说英语，3人既不会说法语也不会说英语，多少名学生会说两种语言．
<gadget id="calculator">30 - 3</gadget>
<output>27</output>

<gadget id="calculator">8 + 16</gadget>
<output>24</output>

<gadget id="calculator">27 - 24</gadget>
<output>3</output>

<result>3</result>