at the end of summer jamie bought a $325 surfboard for $123.50. by what percent was the surfboared marked down

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?

What is coefficient of the term of degree of degree 5 in the polynomial below

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).