N^3=7. what does n equal?

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?

Which one ? is the answer and how to find this answer

Abacteria population is tripling every hour. by what factor does the population change in 1/2 hour? select all that apply