I added my numbers together and divided by the number of numbers but my answer is not a whole number, can that be right? Here are my numbers-75,80,65,90,95,75,90,85,and 75. I added them and got 730. Then I divided by 9 and got 81.1. would that be the mean?

Yes, you did it correctly. There's no rule that says the mean has to be a whole number.

Good job!