I am really confused on how to do this. Please help

How can you construct perpendicular lines and prove theorems about perpendicular lines

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”?

Write the equations in logarithmic form 9^4=6,561