$A$ die is rolled,find the probability that an even number is obtained.

The event $A$ is independent of itself if and only if $P(A) = $

For two events $A$ and $B$,if $P(A) = P(A|B) = 1/4$ and $P(B|A) = 1/2$,then

$A$ bag contains $7$ black and $5$ white balls. $A$ ball is drawn out and replaced in the bag. Then a ball is drawn again. What is the probability that both balls were black?

Three of the six vertices of a regular hexagon are chosen at random. The probability that the triangle formed by these three vertices is equilateral is:

Suppose $n \ge 3$ persons are sitting in a row. Two of them are selected at random. The probability that they are not together is