Please help its in math

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.

Any is very appreciated! (picture is provided below)not sure how to do this at all won't lie

Ineed with math stuff it involves graphs