Question 1147294
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Cancel (n-2)! in both the numerator and denominator.   You will get


    {{{(n*(n-1))/4!}}} = 3,    or


    {{{(n*(n-1))/24}}} = 3.


It is equivalent to


    n*(n-1) = 3*24 = 72.     (1)


Now quickly guess the solution  n = {{{highlight(cross(8))}}} {{{highlight(9)}}}.      <U>ANSWER</U>


     // --- There was a typical "typo" in my original post, which I just fixed here. ---
     //     Thanks to tutors who noticed it (!)


Or, if you want to solve equation (1) algebraically, then please do it . . . 
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