Your answer is: n=-7/2 or n=3/4
all angles = 180 degrees total
add the ratios: 2 +4 +9 = 15
180/ 15 = 12
12*2 = 24
12*4 = 48
12*9 = 108
108 + 48 + 24 = 180
the three angles are: 24, 48 and 108
Go over 9x and that should be it
For every 9 kids 5 are girls
there are 3 sets of 9
so 5 x 3 = 15
there are 15 girls
