A bag contains $12$ red, $15$ blue and $20$ white balls. A ball is drawn at random. Find the probability that the ball is white.

A bag contains $12$ red, $15$ blue and $20$ white balls. A ball is drawn at random. Find the probability that the ball is red or blue.

A bag contains $12$ red, $15$ blue and $20$ white balls. A ball is drawn at random. If the probability that the ball is blue or white is $\frac{m}{n}$, then find the value of $m+n.$

A bag contains $12$ red, $15$ blue and $20$ white balls. A ball is drawn at random. Find the probability that the ball is not white.