Question 34418
Let the number of students in the class be "x".
Number of boys is 0.60x
Number of girls is 0.40x
Later when the 6 boys are added you have
Number of boys is 0.60x+6
Number of girls is 0.40x-6
So the number of students overall has not changed.
Therefore the following equation applies:
EQUATION:
   original # of boys + 6 =  75% of the class
   0.60x + 6 = 0.75x
      6= 0.15x
      x= 40   (Number of students in the class)
    0.6x=24 (original number of boys)
    0.4x=16 (original number of girls)
Cheers,
Stan H.