i passed my 12th class this year with 55 percent marks from C.B.S.E board. My subject is science IE P.C.M.. now i want do study commerce.

Yes you can, one thing i want share with you, study that subject in which you are interested, then study becomes fun and when you opt unlike it becomes hurdle for you. finally in contrast of job, now a days very field has bright future only dedication is required.