Answer: 90%
Step-by-step explanation: To find the probability of not choosing a red marble, we need to calculate the total number of marbles in the bag and subtract the number of red marbles. The total number of marbles is 3 red + 3 green + 15 yellow + 9 purple = 30. So, the probability of not choosing a red marble is P(not red) = (30 - 3) / 30 = 27 / 30 = 9 / 10=90/100=90%