Is there any way to solve this without using the quadratic formula/completing the square? I know that these are some easy ways to do this but I want to know if there is some shortcut that I'm missing out on. If you can't think of one, don't just give me the answer, because I can get that.

Answer this question only if you know the answer! 30 points and

Find the constant of variation for the relation and use it to write an equation for the statement. then solve the equation.

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”?