The sample space for a single die roll is {1,2,3,4,5,6}
The number of possible events = 6
Let's look at the events.
1) Occurrence of an even number:
Favourable outcomes = {2,4,6}
Number of favourable outcomes = 3
Probability = 36=12
2) Occurrence of a multiple of 3:
Favourable outcomes = {3,6}
Number of favourable outcomes = 2
Probability = 26=13
3) Occurrence of a number ≤ 4:
Favourable outcomes = {1,2,3,4}
Number of favourable outcomes = 4
Probability = 46=23