What is the value of X for this equation?

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.

Henry is an avid reader, he devours 90 pages in half an hour how many pages has henry read per minute?

The area of square garden is 300m squared. how long is the diagonal?