3x + 5x + 8y i dont know how to do this plzz

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”?

Ineed the solution to this problem and the steps.

The directions on a sewing pattern say to cut an extra 15% of fabric to account for error. chloe needs 0.75 yard of fabric to make a skirt, and she cuts 0.1125 yard. did chloe cut the correct amount of fabric? why or why not? a. chloe cut enough fabric because she cut the amount of fabric for the skirt. b. chloe cut enough fabric because she cut enough fabric for the skirt and the amount of extra fabric. c. chloe did not cut enough fabric because she only cut the amount of fabric for the skirt. d. chloe did not cut enough fabric because she only cut the amount of extra fabric.