For class A:

Total students=25

Students passed with first class=20

So fraction of students in class A who passed with first class = students passed with first class/total students

Therefore ,Fraction=20/25=4/5

For class B:

Total Students=30

Students passed with first class=24

So fraction of students in class A who passed with first class = students passed with first class/total students

Therefore ,Fraction=24/30=4/5

Hence the both classes have equal fraction of those students who passed with first class.