What property does this equation show? 25 + (6+5)=(25+6)+5

Will give a: 122 b: 90 c: 48 d: 180

What 620000 divided by 10 to the third power

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?