A bag contains 6 red marbles, 4 blue marbles, and 5 green marbles. If one marble is randomly selected, what is the probability that it is NOT red?
✓ Correct Answer: Option C
Total marbles = 6+4+5=15. Marbles that are not red (blue or green) = 4+5=9. Probability = 9/15, which simplifies to 3/5.