A. All remaining numbers are in Q because it goes "even" left, and "odd" right.
B. Probability of it not being in Q is 1/2
The answer is 4/12
That easy
I believe the answer you are looking for is 2.
45 divided by 50= 90%
0.9*16.50=14.85
Notice that the box has a total os 4 + 5 + 3 = 12 balls, since there are 4 that are yellow, then, the probability to randomly obtaining a yellow ball in a single draw is:

therefore, the probability is 0.33 = 33%