What is the rate of change of y with respect to x for this function?

Apatient is given 50 mg dose of medicine the medicines effectiveness decreases every hour at a constant rate of 40% what is the exponential decay function that models this scenario how much medicine will be left in the patients system after 2 hours

What is the rate for one gallon of gasoline

Car a and car b were in a race .the driver of car b claimed that his car was twice as fast as car a