Answer:
(6.2, 8.8)
Explanation:
The Empirical Rule states that, for a normally distributed random variable:
Approximately 68% of the measures are within 1 standard deviation of the mean.
Approximately 95% of the measures are within 2 standard deviations of the mean.
Approximately 99.7% of the measures are within 3 standard deviations of the mean.
In this problem, we have that:
Mean = 7.5 hours
Standard deviation = 1.3 hours
About 68% of adults:
Within 1 standard deviation of the mean. So
7.5 - 1.3 = 6.2 hours
7.5 + 1.3 = 8.8 hours.
So the answer is (6.2, 8.8).