Hello Gurjot, 

If you are from Arts background and you want to pursue B.Com from Delhi University it is only possible to do so if you had Mathematics in class XI and XII as well. However 2.5% will be deducted from your overall percentage of best of four subjects due to stream change. But if you had Mathematics in class XI and XII you can apply for B.Com Hons.

However, if you did not have Mathematics, you can still go for B.Com (program) again with the deduction of 2.5% due to stream change.

I hope this was helpful!