Dear Shruti,
St. Xaviers take admission in both merit and entrance based, if you want to take admission in BA, Bcs, Bcom then your admission will be done on the merit based and if you take admission in BMM and BMS then you need to give the entrance exam.
As you wanted to take admission in Bcom so your admission will be done on the merit based. You need minimum 45% in your 10+2 to be eligible for the application form.
You can apply the form for B.com only in offline mode i.e. by filling up and submitting a form, and through an interview with the Vice Principal of the Commerce section. You can easily get the application form in the office by paying the amount of Rs. 320.
Hope you find it useful, Good Luck :)
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile