What can 25 and 3 both be divided by​

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?

Having a hard time understanding this question (see attachment).

Write 5(6x+4)-2(5x-2) in the form a(bx+c) where a,b and c integers and a> 1