From $21$ tickets numbered $1, 2, 3, \ldots, 21$,one ticket is drawn at random. Find the probability that the ticket drawn has a number divisible by $3$.

Study the given information carefully to answer the question that follows. An urn contains $4$ green,$5$ blue,$2$ red,and $3$ yellow marbles. If $2$ marbles are drawn at random,what is the probability that both are red or at least $1$ is red?

If a number of two digits is formed with the digits $2, 3, 5, 7, 9$ without repetition of digits,what is the probability that the number formed is $35$?

The word '$UNIVERSITY$' is arranged randomly. Then the probability that both '$I$'s do not come together is:

$2$ dice are thrown. Find the probability of getting a sum of at least $10$.

$A$ basket contains $4$ red,$5$ blue,and $3$ green marbles. If three marbles are picked at random,what is the probability that either all are green or all are red?