Answer:
4/15
Step-by-step explanation:
There are red, green and blue marbles in the bag. The total of all the probabilities of selecting red, green and blue marbles is 1.00, or just 1.
So, to find the probability of selecting a blue marble, we add together 1/3 and 2/5 and subtract the total from 1:
1 - (1/3 + 2/5)
or:
1 - (5/15 + 6/15)
or:
1 - 11/15, or 4/15 (answer)