When a dice is thrown, the possible number of outcomes are 6 which are 1, 2, 3, 4, 5 and 6.
(a) Of the total outcomes 2, 3 and 5 are prime numbers. So outcomes of an event of getting a prime number are 2, 3 and 5.
(b) Outcomes of an event of not getting a prime number are 1, 4 and 6.