The other root of the quadratic will be the conjugat of the given root...your polynomila will look like this:
(x - (3 + sqrt 7)) * (x-(3-sqrt 7))
= x^2 - 3x + x sqrt 7 -3x +9 - 3 sqrt 7 - sqrt 7x + 3 sqrt 7 - 7
= x^2 -6x +2 Now I think YOU can put in x = 2 to find the value in the numerator of your question
then put in x = 3 for the denominator..... Let me know what you find !
I will assume you mean the elevation in relation to sea level....
I do not know why they gave you City A stats....sometimes Q's give information to mislead ya or to make sure you know what you are doing....
Part A Dlevel = 1/4 Clevel
= 1/4 (-24) = -6 ft which is the same as saying = 6 ft BELOW sea level (this is Part B)