HELP PLEASE this is due tomorrow for me!!

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.

Ineed with number 6 , explain how to get 1978

Aline passes through 3,7 and 6,9 what equation represents the line