What property is this 1 + 2 = 2 + 1

Answer this question! 30 points and brainliest! only if you know the answer.

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?

Witch represents the inverse of the function f(x)=1/4x-12