The sum of Jahiem and his sister's age is 21. If Jahiem is 7 years older than his
sister, write and solve a system of equations using ) to represent Jahiem's age and s
to represent his sister's age

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”?