Which expression has a value of -10?

a.−5+(−2)+22÷(−2)

b.−2×5−20

c.−3×5−(−8)

d.4×(−3) + 10÷5

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”?