$A$ bag contains $5$ white,$7$ black,and $4$ red balls. If three balls are drawn at random from the bag,what is the probability that all three balls are white?

$A$ box contains $8$ red, $3$ white and $9$ blue balls. If $3$ balls are drawn from the box at random one after the other without replacement, then the probability that they are $2$ red balls and $1$ white ball is

All the spades are taken out from a pack of cards. From these cards,cards are drawn one by one without replacement until the ace of spades comes. The probability that the ace of spades comes in the $4^{th}$ draw is

$A$ bag contains $4$ white and $3$ red balls. Two draws of one ball each are made without replacement. Then the probability that both the balls are red is

$A$ bag contains $5$ brown and $4$ white socks. $A$ man pulls out two socks. The probability that these are of the same colour is

The coefficients $a, b$ and $c$ of the quadratic equation $ax^{2} + bx + c = 0$ are obtained by throwing a die three times. The probability that this equation has equal roots is