What is the slope of the line?

For the equations below which statement is true ?

Solve 2x+y=3 x+y=5 in substitution method

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?