What is the average age of all students.
select avg ( age ) from student
The first name for the student older than the average age.
select fname from student where age > ( select avg ( age ) from student )
Give me the count for the students older than the average age.
select count ( fname ) from student where age > ( select avg ( age ) from student )
Give me the count for the students younger than the average age.
select count ( fname ) from student where age < ( select avg ( age ) from student )
Give me the count for all students
select count ( fname ) from student