PLS HELP ME ASAP PLS AND TY

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.

There are 45 questions on your math exam. you answered 810 of them correctly. how many questions did you answer correctly?

Cody was 165cm tall on the first day of school this year, which was 10% taller than he was on the first day of school last year.