She can make a total of 30 different outfits, just multiply them all together.
The geometric sequence is 3, 9, 27, 81, 243, 729 because each time it is multiplied by 3.
The question says boys/girls = 3/4 so if there are 12 boys in the class you can say:
3/4 = 12/?
and ? is the number of girls which is equal to:
? = 12*3/4 = 9
so if there are 12 boys in the class we will have 9 girls in the class :)))
i hope this is helpful
have a nice day