A vector X is added to vector Y = 12 i -16 j. The resultant vector lies along the positive x-axis and has the same magnitude as X. What is the magnitude of X? (Note: symbols in bold type are vectors).

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”?