First of all, you could just add it all up and divide it by 16, but if you want to do it the formula way, you can do this:

1) to find the sum of 75 + 76 + 77 + 78 + 79 + 80 + 81 + 82 + 83 + 84 + 85 + 86 + 87 + 88 you want to do \(\frac{((75+88)(14))}{(2)}\) and then you'd be able to figure out the answer for the sum.

2) Just divide the answer by 16.

By the way, I'm not going to tell you the answer. I honestly think that you will be able to solve this on your own. Good Luck!!!!