What is 1+2+3+4+5+6+7+8+9

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”?

Iknow its nothing to do with education, but what type of thing should i wrote here? ? : ) its for mcdonald's btw.

The sum of the speeds of two trains is 720.2 mph. if the speed of the first train is 7.8 mph faster than the second train, find the speeds of each.