It cost Faith $9.10 to send 91 text messages. How many text messages did she send if she spent $17.60?

What is the average rate of change for this function for the interval from x=2 to x=4 ?

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?

Icould really use some with this question.