Anumber cube is rolled. what is p(3 or an even number)

In order to find the probability of a 3 or an even number, we must add the probabilities of the individual events. This is done as:
P(3) = 1/6
P(even number) = 3/6 = 1/2

P(3 or even number) = 1/6 + 1/2
P(3 or even number) = 2/3

What are the following algebraic equations. you need to post those if you want the answer