Among the 100 passengers, 70 understand English, 65 understand Japanese, 45 understand both English and Japanese, and how many people understand neither English nor Japanese.
在100位旅客中，有70人懂英语，65人懂日语，既懂英语又懂日语的有45人，既不懂英语又不懂日语的有多少人．
<gadget id="calculator">65 - 45</gadget>
<output>20</output>

<gadget id="calculator">70 + 20</gadget>
<output>90</output>

<gadget id="calculator">100 - 90</gadget>
<output>10</output>

<result>10</result>