Answer:
There are 8 red marbles
Step-by-step explanation:
Let the number of red be R , number of yellow be Y , number of orange be O and number of white be W. Then
..................... *
Half the number of red implies : 
Two less than the number of yellow implies : 
A third the number of orange implies : 
A third of three more than the number of white marbles implies : 
combining everything together , we have

implies :
................ equation 1
implies : 
therefore:
...................... equation 2
implies : 

Therefore:
......................... equation 3
Substituting equation 1 ,2 and 3 into equation * , we have






substitute the values of Y , to get R , O and W










Therefore:
number of red = 8
number of yellow = 6
number of orange = 12
number of white = 9