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

$A$ box contains $15$ black and $20$ white balls. What is the probability that when $2$ balls are selected,both are white?

One bag contains $4$ white balls and $2$ black balls; another contains $3$ white balls and $5$ black balls. If one ball is drawn from each bag,find the probability that both are white.

The probability of an event $A$ occurring is $0.5$ and that of $B$ is $0.3$. If $A$ and $B$ are mutually exclusive events,find the probability that neither $A$ nor $B$ occurs.

$A$ bag contains $3$ red balls,$5$ yellow balls,and $7$ pink balls. If one ball is drawn at random from the bag,what is the probability that it is either pink or red?

Study the given information carefully and answer the questions that follow: $A$ basket contains $4$ red,$5$ blue and $3$ green marbles. If $3$ marbles are picked at random,what is the probability that at least $1$ is blue?