Why are the solutions to the proportions 50/x = 10/20 and 10/50 = 20/× the same?

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.

Whats the name of the vertical axis

Acredit card advertises an annual interest rate of 23%. what is the equivalent monthly interest rate?