Help! What does z equal??

Write a corresponding real world problem to represent 2x - 125=400

Brainlest answer can you find the area and circumference of a circle given the radius or diameter? if its yes or no explain why

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.