Math help please urgent

Which formula gives the area of a triangle? a=1/2(b+h)

What is the length of the segment joining the points at (4,5) and (6,-2) round to the nearest tenth if necessary

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?