how do actually solve the problem below ? still confused

Question

anonymous · Answer

Scores on a university exam are Normally distributed with a mean of 68 and a standard deviation of 9. Using the 68-95-99.7 rule, what percentage of students score above 77?
A.	2.5%
B.	5%
C.	16%
D.	32%

how do exactly solve this problem? still confused

anonymous · Answer

one standard deviation above the mean 68 is 77 and one standard deviation below is 59. using the 68-95-99.7 rule, 68% of the scores are between 59 and 77.

that means 32 % are below 59 and above 77. The question is just asking for scores above 77 so half of 32% is 16 %

anonymous · Answer

confused on what equation i use to get the answer ?

anonymous · Answer

to find the percent of scores above 77 (which is one standard deviation, 9,  over the mean, 68) you do (100-68)/2