Please help

-2/5-4/5+(-9/10)

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Issof claims that the scale factor is 1/2. which statement about his claim is correct

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”?

Segment wx is shown explain how you would construct a perpendicular bisector of wx using a compass and a straightedge