Find x, y, and z . Similarity in triangles geometric mean. Need help with questions 8 and 9

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?

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

*let m∠cob = 50°30’, m∠aob = 70° and m∠aoc = 20°30’. could point c be in the interior of ∠aob? why?