Hey,
The eligibility criteria to pursue Bachelor of Arts in Economics is to have Mathematics or Business Business Mathematics as one of the subjects at 12th level. So,if you must include Mathematics in the best four. The eligibility of the same requires the candidates to have passed Senior Secondary School Certificate Examinations of the central board of secondary education,New Delhi with a pass in four subjects(English,Mathematics and two elective subjects).
If you are planning to pursue BA Honours in Economics in Delhi University,then 81 percent in best four will not get you any good college as most of the colleges have very high cutoff.
Hope this helps.
Good luck.