Hii Abhipsa

Yes it is mandatory/compulsory for you to add your marks secured by you in english in your class 12th boards examinations when your are applying for admissions to the University of Delhi ,New delhi. As for you are applying for the Bacehlor's of sciences in Mathematics Honours you have to add your maths marks as well as english these wo are compulsory to be added while calculating your best of four percentage.

Hope it helps

Thanks