Help me plz it homework

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.

Acircle has a circumference of 28.36 units what is the diameter of the circle

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?