If four persons are chosen at random from a group of $3$ men,$2$ women,and $4$ children,then the probability that exactly two of them are children is:

$A$ 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 the balls drawn were white?

$1$ bag contains $4$ white and $2$ black balls. Another bag contains $3$ white and $5$ black balls. If $1$ ball is drawn from each bag,find the probability that both balls are black.

In a simultaneous throw of three coins,what is the probability of getting at least $2$ tails?

The probability that a man will be alive $25$ years hence is $0.3$,and the probability that his wife will be alive $25$ years hence is $0.4$. Find the probability that $25$ years hence,only the woman will be alive.

Two dice are thrown simultaneously. What is the probability of obtaining a multiple of $2$ on one of them and a multiple of $3$ on the other?