Help help help help math

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

286 divided by 457.6 what is the quotient?

How many four digit even numbers can be formed from digits 1,2,3,4,5 if repetition is allowed. how can solve this using permutation formula