If $A$ and $B$ are two independent events,then $P(A/B) = $

Three dice are thrown simultaneously. What is the probability of obtaining a total of $17$ or $18$?

Fifteen persons,including $A$ and $B$,sit down at random at a round table. The probability that there are $4$ persons between $A$ and $B$ is

$A$ bag contains $6$ red,$5$ white and $4$ black balls. Two balls are drawn. The probability that none of them is red,is

An unbiased die is tossed until a number greater than $4$ appears. The probability that an even number of tosses is needed is

$A$ box contains $6$ black and $4$ red balls. Three balls are drawn at random. What is the probability that one ball is red and the other two are black?