When two dice are thrown,what is the probability of getting a sum of $7$ (in $/36$)?

Three coins are tossed. Describe three events which are mutually exclusive and exhaustive.

$A$ coin is tossed and a die is thrown. The probability that the outcome will be a head or a number greater than $4$ or both,is

Three persons $P, Q$ and $R$ independently try to hit a target. If the probabilities of their hitting the target are $\frac{3}{4}, \frac{1}{2}$ and $\frac{5}{8}$ respectively,then the probability that the target is hit by $P$ or $Q$ but not by $R$ is

$A$ man and a woman appear in an interview for two vacancies in the same post. The probability of the man's selection is $1/4$ and that of the woman's selection is $1/3$. What is the probability that none of them will be selected?

Two dice are rolled simultaneously. The probability that the sum of the two numbers on the dice is a prime number is: