What is the percent of change from 85 to 64

Monthly water bills for a city have a mean of $108.43 and a standard deviation of $32.09. find the probability that a randomly selected bill will have an amount greater than $155, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)

Ineed with number 6 , explain how to get 1978