Mike is selecting one Rose and not putting it back. We want to multiply the probability of selecting a white rose out of the total by the probability of selecting a yellow rose out of the total minus the already selected one. We are multiplying because the probability is an and scenario.
7 + 8 + 9 = 24 total roses
9 / 24 x 8 / 23 = 72 / 552
Hope this helps!! :)