If $P(A) : P(\overline{A}) = 4 : 1$,then $P(\overline{A}) = \ldots$

$A$ carton of $24$ bulbs contains $6$ defective bulbs. One bulb is drawn at random. What is the probability that the bulb is not defective? If the bulb selected is defective and it is not replaced, and a second bulb is selected at random from the rest, what is the probability that the second bulb is defective?

Two dice are thrown at the same time. Determine the probability that the difference of the numbers on the two dice is $2$.

There are $5$ white, $7$ red, $4$ black, and $2$ blue identical balls in a box. One ball is selected at random from the box. Find the probability that the ball is either black or white.

Total number of outcomes in the experiment of throwing a balanced die twice is ..........

An unbiased coin is tossed thrice. Find the probability of the following event:
$A:$ Exactly $2$ heads are received.