Probability of any event $x$ lies

A pair of fair dice is rolled together till a sum a either 5 or 7 is obtained. If p denoted the probability that 7 comes before 5, find 15p

The probability that $A, B$ and $C$ can solve a problem are $\displaystyle \frac{4}{5}, \frac{2}{3}$ and $\dfrac{3}{7}$ respectively. The probability of the problem being solved by $A$ and $B$ is $\dfrac{8}{15}$, $B$ and $C$ is $\dfrac{2}{7}$, $A$ and $C$ is $\dfrac{12}{35}$. The probability of the problem being solved by all the three is $\dfrac{8}{35}$.

Find the probability that the problem can be solved by at least one of them.

If $P(A)-p(A')=0.5$, then $P(A)=$____