Given $P(A) = \frac{3}{5}$ and $P(B) = \frac{1}{5}$. Find $P(A \text{ or } B)$,if $A$ and $B$ are mutually exclusive events.

If a card is drawn at random from a well-shuffled pack of $52$ playing cards,then the probability that it is either an ace or a spade card is

The odds against a person who is $40$ years old living until he is $70$ are $8$ to $5$,and the odds against another person who is $50$ years old living until he is $80$ are $4$ to $3$. Find the probability that exactly one of them will be alive $30$ years from now.

When two dice are thrown once,find the odds against getting a sum of $7$ on the two dice.

Twelve tickets are numbered $1$ to $12$. One ticket is drawn at random,then the probability of the number being divisible by $2$ or $3$ is:

If $A$ and $B$ are any two events,then $P(A \cup B) = \dots$