Among the 30 students, 18 can speak French, 16 can speak English, and 3 can neither speak French nor English. How many students can speak two languages?
30名学生中，18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">18 + 16</gadget>
<output>34</output>

<gadget id="calculator">30 - 3</gadget>
<output>27</output>

<gadget id="calculator">34 - 27</gadget>
<output>7</output>

<result>7</result>