One of the fractions could be 1/2
Hoped this helped at all :)
Assuming that each marble can be picked with equal probability, we notice that there is a total of

marbles, of which 2 are red.
So, the probability of picking a red marble is

In fact, as in any other case of (finite) equidistribution, we used the formula

-a is 302,-45,108,125
idk the rest tho