What are the two non-graphical methods for solving systems of equations

Plzzz i beg u so much asaaaap ! what is the slope of this line? enter your answer in the box.

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?

Ineed with math stuff it involves graphs