select distinct student   
from   enrolls,teachers,sections   
where  exists   
      (select *   
       from enrolls,teachers,sections   
       where teachers.teacher=sections.teacher and sections.course=enrolls.course and teachers.teachername='Dr.Lowe'   
       group by student   
       having count(distinct enrolls.course)=(select count(distinct enrolls.course)   
                                   from enrolls,teachers,sections   
                                   where teachers.teacher=sections.teacher and sections.course=enrolls.course and teachers.teachername='Dr.Lowe')