Solution of problem N4514 probability theory

Solution of problem N4514 probability theory

4514. The urn contains 3 green and 4 red balls.
a) Two balls are taken out of the urn at the same time. Find the probability that they are the same color.
b) What event, provided that two balls are taken out of the urn at the same time, is more likely: A - "balls of the same color", B - "balls of different colors"?

Additional information:

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