What is the value of x in the equation 1/5 x – 2/3 y = 30, when y = 15?
a.4
b.8
c.80
d.200

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.