System of Linear Equations (Substitution Method)

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.

How to use order of operation in 20 divide by 4 multiply 5 = 1

Ten times the square of a non-zero number is eqaul to ninety times the number