•in fraction form the answer is 2/15
•in percentage form the answer is 13.33333333...%
the way to figure this out is to add all the numbers up and divide it by the number of red marbles :)
        
             
        
        
        
Let Xavier's favourite fraction be a/b, Yessie's favourite fraction = b/a and Zorro's favourite fraction = c/d,
c/d x a/b = 12/35 . . . . . . . . (1)
c/d x b/a = 15/7 . . . . . . . . (2)
(1) x (2) = c/d x a/b x c/d x b/a = 12/35 x 15/7
 c^2 / d^2 = 36/49
c^2 = 36
c = 6
d^2 = 49
d = 7
Xaviers favourite fraction = 12/35 / 6/7 = 2/5 
Yessies favourite fraction = 5/2
Zorro favourite fraction = 6/7
        
             
        
        
        
What's 1/3 of 12?
Mulitply 1/3 times 12 = 4
Nita uses 4 eggs.
        
             
        
        
        
3rd one 10 x 6 x 6
hope this is right