What is the course id for the prerequisite of that course?
SELECT course_id FROM course WHERE course_id IN  ( SELECT T1.prereq_id FROM prereq AS T1 JOIN course AS T2 ON T1.course_id  =  T2.course_id WHERE T2.title  =  'International Finance' ) 
prerequisite of a course refers to prereq_id related to that course; course id for the prerequisite refers to SELECT course_id WHERE course_id = prereq_id;