Ineed ill mark brainilist to best answer

Me with this one question, and i'll upvote the brainliest answer

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”?

Atriangle has side lengths of x, x+11, and 3x+5. what is the perimeter?