Which equation has exactly one solution. a 7x=7, b 7x=7x, c x+1=x+1, d x+1=x+2

Monthly water bills for a city have a mean of $108.43 and a standard deviation of $36.98. find the probability that a randomly selected bill will have an amount greater than $173, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?