Answer: Hello there!
initially Maria has 6 red marbles, 6 blue marbles, and 4 green marbles.
You know that in the first pick, Maria gets a green marble ( this means that now there are 3 green marbles left)
Now we want to know the probability that she gets a red marble on the second pick.
Now there are 6 + 6 + 3 = 15 marbles in the bag, and 6 of them are red ones. Then the probability of getting one red is the number of red ones divided by the total amount ( which is the ratio of red marbles to total marbles)
this is 6/15.
now you can see that there is no 6/15 in the options, so we need to see which one is equivalent.
if we took the option C, 2/5, and multiply both denominator and numerator by 3, we get (3*2)/(3*5) = 6/15, then 2/5 and 6/15 are equivalents.
Then the correct answer is C.
