1.1 Introduction and Definitions

1. Set. The rule is clear. Elements are $\{January, June, July\}$. We can definitely say 'August' is not in the set. 2. Not a Set. "Most talented" is vague and subjective. One person's choice differs from another's. 3. Set. The elements are $\{1, 2, 3, ..., 99\}$. The condition is mathematically precise.