Ecuation
3x-5y=9
2x+7y=-56

(98 points) i need with 5 questions. answer definitions are welcomed, but not necessary.

Suppose that the price p (in dollars) and the weekly sales x (in thousands of units) of a certain commodity satisfy the demand equation 4p cubedplusx squaredequals38 comma 400. determine the rate at which sales are changing at a time when xequals80, pequals20, and the price is falling at the rate of $.20 per week.

Jordan got 27 out of 90 correct on his test . what fraction of the marks did her get correct