If the odds against an event be $2 : 3$,then the probability of its occurrence is

In a single toss of a fair die,the odds against the event that number $4$ or $5$ turns up is

$A$ card is drawn from a pack of $52$ cards. Find the probability that the card will be a queen or a heart.

If two events $E_1$ and $E_2$ are such that $P(E_1 \cup E_2) = \frac{5}{8}$,$P(\bar{E}_1) = \frac{3}{4}$,and $P(E_2) = \frac{1}{2}$,then $E_1$ and $E_2$ are:

$A$ coin is tossed twice. If events $A$ and $B$ are defined as: $A = \text{head on first toss}$,$B = \text{head on second toss}$. Then the probability of $A \cup B = $

If the odds against $A$ solving a problem are $4:3$ and the odds in favor of $B$ solving the problem are $7:5$,what is the probability that only one of them solves the problem?