Which of the following expressions represents the distance between -3.9 and -4.7

A: -4.7 - 3.9

B: -3.9 - 4.7

C: None of the above

Can someone me with this problem . show your work .

How do i do this activity, is appreciated

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?