Pls help

If f(x)=x^3 and g(x)=2x+7 when g(x)=-5

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.

What is the value of m in the equation 1/2 m - 3/4n=16 when n=8