Question 1161210
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The number of those who plays at least one sport is 21 - 11 = 10.


Therefore, the number of those who plays both sports is  7 + 8 - 10 = 5.


The probability under the problem's question is  P = {{{5/21}}}.    <U>ANSWER</U>
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Solved.


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To understand the solution in FULL, read and learn from the lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/misc/Counting-elements-in-sub-sets-of-a-given-finite-set.lesson>Counting elements in sub-sets of a given finite set</A>

in this site.



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