Can somebody help me please ​

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.

There are 45 questions on your math exam. you answered 810 of them correctly. how many questions did you answer correctly?

y=2x−1 5x−4y=1 is (1,1)(1,1) a solution of the system?