I'm a maths stream student. Can I do BBA+MBA? Can I get good career prospects after doing BBA+MBA as I am a science student?

First of all, yes, you can go for BBA+ MBA. And, if you are from Science background then it will surely help you in BBA and MBA this will provide you best opportunities. So, I suggest you to go for it.

You can definitely go for BBA and MBA. This provides ample of opportunities to explore once you have a degree. A stream does not matter for BBA and MBA but it will be a little bit difficult.