The empirical rule states that in a normal distribution, 68% of data is within 1 std deviation of the mean 95% of data is within 2 std deviation of the mean 99.7% of data is within 3 std deviation of the mean
In this case 95% of the cases would be within two std deviations of the mean mean - 8 and mean + 8 72 - 8 = 64 and 72 + 8 = 80
then 95% of the scores are between 64% and 80% on the test.
