How do I find an overall grade?

My scores are:

27.92 out of 30
19.25 out of 17.5
21.88 out of 17.5
11.55 out of 17.5
13.65 out of 17.5

The two scores I got bonus questions right that's why I scored above.

Can you please explain how to get the answer so I can know how to solve!

I have 6 tests left is it still possible to get an A in this class?​