The sample space is {1,2,3,4,5,6} A. The only prime numbers in the sample space are 2,3 and 5. That's 3 ways out of 6 ways that a prime number can be be rolled. "Out of" means "over", so the probability is 3 over 6 or 3/6 and that reduces to 1/2. B. The only odd numbers in the sample space are 1, 3 and 5. That's 3 ways out of 6 ways that a odd number can be rolled. "Out of" means "over", so the probability is 3 over 6 or 3/6 and that reduces to 1/2. Edwin