How would I answer this question?

Answer:
a. Here are all the possible outcomes:
2 times red
2 times green
2 times white
1 time red, 1 time green
1 time green, 1 time white
1 time red, 1 time white
b. 1; If you look above, the combination of red and green only exists once
c. 3; If you look above, there are 3 combinations that don't contain white in it and they are 2 times red, 2 times green, and 1 time red, 1 time green.