Which students attended the course with course id 301?
select student_id from student_course_attendance where course_id = 301
Count how many did so.
select count(*) from student_course_attendance where course_id = 301
What about the course English?
select count(*) from courses as t1 join student_course_attendance as t2 on t1.course_id = t2.course_id where t1.course_name = "English"