Question 860139
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Hi,
Let x represent the original number of students in group
{{{$120/x -$2 =  120/(x+2) }}}    |Multiplying thru by x(x+2) so as all denominators = 1
 120(x+2) - 2x(x+2) = 120x
 120x + 240 - 2x^2 - 4x = 120x
    2x^2 + 4x - 240 = 0
     x^2 + 2x - 120 = 0    (Tossing out the negative solution for unit measure)
   (x +12)(x-10) = 0
           x = 10, the original number of students in group
CHECKING our answer***
 $12 - $2 = $120/12 = $10
Wish You the Best in your Studies.