In a game of throwing a die,what is the probability of getting a $1$ on an even-numbered throw?

If a man throws a die until he gets a number bigger than $3$, then the probability that he gets a $5$ in his last throw is

$A$ box contains $b$ blue balls and $r$ red balls. $A$ ball is drawn randomly from the box and is returned to the box with another ball of the same colour. The probability that the second ball drawn from the box is blue,is

Cards are drawn one-by-one without replacement from a well-shuffled pack of $52$ cards. The probability that a face card (jack, queen, or king) will appear for the first time on the third turn is equal to:

$U_1, U_2, U_3$ are three urns. $U_1$ contains $5$ red,$3$ white,$2$ black balls; $U_2$ contains $4$ red,$4$ white,$2$ black balls and $U_3$ contains $3$ red,$4$ white,$3$ black balls. If a ball is chosen at random from an urn chosen at random,then the probability of not getting a black ball is

$A$ and $B$ are independent events with $P(A)=\frac{1}{4}$ and $P(A \cup B)=2 P(B)-P(A)$,then $P(B)$ is