What is the probability that when one die is thrown,the number appearing on top is even?

$A$ bag contains $3$ red and $7$ black balls. Two balls are taken out at random,without replacement. If the first ball is red,what is the probability that the second ball is also red?

$A$ coin is tossed until a head appears or until the coin has been tossed five times. If a head does not occur on the first two tosses,then the probability that the coin will be tossed $5$ times is

$A$ problem in Statistics is given to four students $A, B, C$ and $D$. Their chances of solving it are $\frac{1}{3}, \frac{1}{4}, \frac{1}{5}$ and $\frac{1}{6}$ respectively. What is the probability that the problem will be solved?

$A$ box contains $6$ nails and $10$ nuts. Half of the nails and half of the nuts are rusted. If one item is chosen at random,what is the probability that it is rusted or is a nail?

$A$ box contains $36$ tickets numbered $1$ to $36$. One ticket is drawn at random. Find the probability that the number on the ticket is either divisible by $3$ or is a perfect square.