Urn 1 contains 7 red balls and 1 black ball. Urn 2 contains 1 red ball and 2 black balls. Urn 3 contains 5 red balls and 2 black balls. If an urn is selected at random and ball is drawn, find the probability that it will be red.
There are 30 students in a class of Mr. Obniarillo. 18 are boys and 12 are girls. What is the probability of
choosing a random student?