Sort:  

Sorry, but the correct answer is 15 Creepy Birds. The logic for this is:
6C = 2R + 4D
9D = C + 4F
3Q = 3R + 3C + D
7C + Q = 4R + 4D

(14/6)R + (28/6)D + Q = 4R + 4D
Q = (5/3)R - (⅔)D
D = 3Q - 3R - 3C
D = 5R - 2D - 3R - 3C
3D = 2R - 3C
6C = 4R - 6D
4R - 6D = 2R + 4D
R = 5D
6C = (14/5)R
30C = 14R
15C = 7R

Values of each:
R = 15
C = 7
D = 3
F = 5
Q = 23

I would add my logic but even I'm not sure I can follow all my equations. I did break it down to 3 rainbow = 3/2 creepy - 1/2 rainbow which leads to 7 rainbow for 3 creepy.