Question 298712
c+f+d=450
2f=3c
2c=d
c = 100,   d = 200,   f = 150

The other tutor was ok with x+x/2+3x/4=450

x=200 which is my d
For some reason he multiplied part of the equation by 4 but not all
and got 

4x+2x+3x /4 = 450 
if he had continued correctly

4x+2x+3x  = 1800
 9x=1800
x=200
each fox is 3x/4=600/4=150 which is my f