12 +16 +15 = 43 total marbles
12 are yellow so first pick you have 12/43 probability of picking yellow
without replacement there would be 42 marbles left
there are 16 red ones so you have a 16/42, reduces to 8/21 probability of picking red
probability of picking yellow then red =
12/43 x 8/21 = 96/903, reduces to 32/301 probability
