6 pencils =2 ballpoint pens

1 pen =3 pencils

1 class +2 class =83 people,

Class 3+Class 4 +90 people,

Class 2+Class 3 =85 people

1 Number of classes and 4 classes =83+90-85=88.

6 chess =2 table tennis

3 football =9 table tennis

3 chess = 1 table tennis

1 football =3 table tennis

4 Football = 12 Table Tennis