Mean on a physiological test+ 75, s = 8. You hire a tutor who guarantees scores in the top 5% of the class or your money back. You make an 80. Do you pay?

To be the top 5%, you have to be in the 95th percentile. That is, you score higher than 95% who take the test.

Look up the z-score that corresponds to .95

It is 1.645

x={\mu}+z\sigma

Enter the known data and see what the minimum score has to be in order to score in the top 5%.
If it is higher than an 80, then you do not have to pay.