select STUDENT.S_LNAME, STUDENT.S_FNAME, ENROLLMENT.MARK, COURSE_SECTION.LOC_ID, S_Sex
inner join ENROLLMENT on STUDENT.S_ID = ENROLLMENT.S_ID
inner join COURSE_SECTION on ENROLLMENT.C_SE_ID = COURSE_SECTION.C_SE_ID
where MARK > 70 and exists (select *
where LOC_ID='Bundoora' and S_Sex='Female');
with sub as(select <required_fields> from student_table a where student_id not in(select student_id from <enrollment> where mark< 70)) --Filters out all records with score <70 at any point select S_LNAME, S_FNAME, MARK, LOC_ID, S_Sex from sub inner join ENROLLMENT_A1 on (sub.S_ID = ENROLLMENT_A1.S_ID) inner join COURSE_SECTION_A1 on (ENROLLMENT_A1.C_SE_ID = COURSE_SECTION_A1.C_SE_ID ) where LOC_ID='Bundoora' and S_Sex='Female';
Appropriate modifications based on your input.
Basically, you could filter out all student ids who have ever scored less than 70 using a temporary table, or even in your subselect, and then proceed with your operations.