The following problems require reasoning for their solution. To prove that an answer is correct requires an argument (often containing subsidiary arguments) whose premises are contained in the statement of the problem—and whose final conclusion is the answer to it. If the answer is correct, it is possible to construct a valid argument proving it. In working these problems, readers are urged to concern themselves not merely with discovering the answers but also with formulating arguments to prove that those answers are correct.

Mr. Short, his sister, his son, and his daughter are fond of golf and often play together.
The following statements are true of their foursome:
a. The best player’s twin and the worst player are of the opposite sex.
b. The best player and the worst player are the same age.
Which one of the foursome is the best player?