How many courses have more than one prerequisite?
select count ( * )  from  ( SELECT T1.title FROM course AS T1 JOIN prereq AS T2 ON T1.course_id   =   T2.course_id GROUP BY T2.course_id HAVING count ( * )   >  1 ) 
courses with more than one prerequisite refers to COUNT(*) > 1 in a GROUP BY statement on the prerequisite table; count of such courses is obtained by a SELECT COUNT(*) from a subquery that groups prerequisites by course and filters those having more than one.