Can someone please help 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.

Apackage of five erasers cost 0. $.39 at this rate how many how much would 60 erasers cost in dollars and cents

Luis has a cooler filled with cans of soda.for every 5 cans of coke there are 3 cans of sprite.if there are 25 cans of coke, how mant cans of sprite are there?