The average of 15 test scores is 80. If the average of first eight test scores is 65 and that of the last eight test scores is 70, then the eighth score is 80. True of False?

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?

Don't know how to find x given these segment lengths

Can some one me with these questions