Question

when randomly selecting an​ adult, a denotes the event of selecting someone with blue eyes. what do and ​represent?

Answer 1

The symbol "​" is actually a Unicode character called a "zero-width space" and it has no meaning in this context. However, if you meant to ask what the symbol "a" represents, then "a" represents the event of selecting an adult with blue eyes when randomly choosing from a group of adults.