Hi, You cannot do BBA and BCA together if regular and both course have different career prospects. For BCA maths is a must condition but not most likely for BBA. As in some maths is not a must requirement.

There is an entrance exam for both the courses in most of the colleges.
Based on your stream in class 12th and the subjects you had in 12th you will have to decide which course you are interested to pursue.

BCA-
For graduates, job opportunities exists in Government as well as Private sector. Also, self employment options are available. After BCA., which is an Undergraduate course, graduates may take up Government jobs that require a Graduation Degree (for example- Armed Forces, Nationalized Banks, PSUs etc). When it comes to Private sector, Software MNCs are the prime recruiters. Web hosting, IT sector, Electronics Industry are some other sectors that recruits BCA.
BBA-
In any sector, business administration experts or professionals play a very significant role. The management is the way to reach on the top of the height as soon as possible by using your leadership and working proficiency. A management professional always plays a vital role in his/her company and this is why, he used to keep in touch with the board of directors. All sectors including government and public have various industries, companies, institutions or related organizations, come in the job prospective fields for a management professional.

So accordingly you will have to decide what are your interests and which field to choose as both have good scopes.
Good luck.