What’s the value of k?

Select the quadratic that has root x = 8 and x = -5

For f(x) = 3x+1 and g(x) = x2 - 6, find (g/f)(x)

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”?