Respuesta :

There will be 2 groups, and each group have 6girls and 9 boys.
12 ÷ 2 = 6
18 ÷ 2 = 9
well i think about it like this
I added 12 and 18 together which gave me 30 
right ?
  12
+18
--------
  30

then I divided it by two (you must be wondering why I got the two from, its because we only have two genders 
which is 

30/2 = 15
i hope it helped