Among a group of passengers, there are (3/4) people who know French, (4/5) people who know English, (13/20) who know both languages, and 10 people who don't know both languages. Understand. How many passengers are there in this group?
在一批旅客中，有(3/4)的人懂法语，(4/5)的人懂英语，两种语言都懂的占(13/20)，另有10人这两种语言都不懂．这批旅客有多少名？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">13 / 20</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">(4/5) - (13/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/4) + (3/20)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">10 / (1/10)</gadget>
<output>100</output>

<result>100</result>