What plus -4.52 equals a negative nummber? is it -5.4 or 3.86

What is always true when two whole numbers are subtracted?

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”?

Can you me find the slope! (30 points)