Solution of problem N4580 probability theory

Solution of problem N4580 probability theory

4580. In the urn: 10 white, 2 black and 4 red balls. What is the probability of removing from the urn:
a) black ball
b) green ball
c) the first is white, the second is black balls
d) two red balls
e) the first is white, the second is red, the third is black

Additional information:

Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)