What is the value of x? enter your answer, as a decimal, in the box. cm

Ineed me i stuck and i don’t want to get it wrong

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”?

Which ordered pair is a solution of the equation? 2x+3y=10