The probability for event a is 0.3, the probability for event b is 0.6, and the probability of events a or b is 0.8. the events are not mutually exclusive because the

sum of p(a) and p(b) is less than p(a or b)
product of p(a) and p(b) is less than p(a or b)
product of p(a) and p(b) is not equal to p(a or b)
sum of p(a) and p(b) is not equal to p(a or b)