Please help me idk how to do this

Plz help plz give me the answer

How do i get my dad to stop making me gargle his pickle i want my mom to gargle my pickle not my dads

Let f(x) = 3 − x . find the average rate of change of f(x) from x = a to x = a + h and simplify your answer so that no single factor of h is left in the denominator.