x, y, and z are all unique numbers. If x is chosen randomly from the set {6, 7, 8, 9, 10, 11} and y and z are chosen randomly from the set {20, 21, 22, 23}, what is the probability that x and y are prime and z is not?  Choose the correct answer
A) 1/5 B) 3/20 C) 2/15 D) 1/12 E) 1/10
P(x is prime) = 1/3   P(y is prime) = 1/4   If y is prime, then z is not prime since y and z are unique.   Then the probability is 1/3*1/4 = 1/12   The answer is 1/12.
<result>D</result>
x, y, and z are all unique numbers. If x is chosen randomly from the set {6, 7, 8, 9, 10, 11} and y and z are chosen randomly from the set {20, 21, 22, 23}, what is the probability that x and y are prime and z is not?