What would this average out to

for this semester I received two D's and a B on my tests. if I receive an A or B on my final, what can the total ending grade possibly be?

Depends on your teacher's grading policy.

If everything is equal, then if D = 1, C=2, B=3, A=4 gpa most schools.
1 + 1 + 3 + 4 = 9/4 = 2.25 which is a C-
1 + 1 + 3 + 3 = 8/4 = 2 which is a C

If your final is worth more, then you'll get higher than a C- but your grade wont be a B or higher unless your teacher counts your final like 60,70% which is extremely unlikely.

It depends. Assuming that your D's are 65%, your B is 85%, and all tests are equally weighted and worth 100 points.
The A (Assuming 95%) will get you a final grade of (65+65+85+95)/400= 77.5% (About a C+)
The B (Assuming 85%) will get you a final grade of (65+65+85+85)/400= 75% (About a C)

Good luck and get studying

Depends what percentage your grades are worth.

IF YOU GET AN A OR B, YOUR LOOKING AT A C-GOOD LUCK