For two events $A$ and $B$,if $P(A) = P(A|B) = \frac{1}{4}$ and $P(B|A) = \frac{1}{2}$,then:

Let $X$ and $Y$ be two events of a sample space such that $P(X)=\frac{1}{3}$,$P(X|Y)=\frac{1}{2}$ and $P(Y|X)=\frac{2}{5}$,then which of the following is true?

Find $P(E | F)$ for a die thrown three times,where $E: 4$ appears on the third toss,and $F: 6$ and $5$ appear respectively on the first two tosses.

If $A$ and $B$ are any two events such that $P(A) + P(B) - P(A \cap B) = P(A)$,then $\dots \dots \dots$

Assume that each born child is equally likely to be a boy or a girl. If a family has two children,what is the conditional probability that both are girls given that at least one is a girl?

If $2 P(A) = P(B) = \frac{5}{13}$ and $P(A \mid B) = \frac{2}{5}$,then $P(A \cup B) = $ . . . . . . .