In the problem, the mean is:
[tex]mean=98.25F[/tex]And the standard deviation:
[tex]SD=0.68F[/tex]We want to use the empirical rule to find which percentage of the data falls in the interval 96.89F - 99.61F
let's see how far from the mean are these values.
Let's add the standard deviation to the mean once:
[tex]98.25+0.68=98.93F[/tex]Let's add a standard deviation again:
[tex]98.63+0.68=99.61F[/tex]This is the right end of the interval. Is 2 standard deviations from the mean.
Let's do the same with the left end of the interval. If we subtract a standard deviation from the mean:
[tex]98.25-0.68=97.57F[/tex]Once again:
[tex]97.57-0.68=96.89F[/tex]Thus, we just saw that the interval 96.89F-99.61F is the data that is within 2 standard deviation from the mean.
The empirical rule tell us that, in a normal data set 95% of the data is within 2 standard deviations from the mean.
Thus, the percentage of adults with temperatures between 96.89F and 99.61F is 95%