I am a college student I am trying to do math reasonning

Which expression is equivalent to? assume x > 0 and y > 0.

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?

Explain how you can use the associative property to evaluate (7x50)x4.