(goh)(x) = (g(x))(h(x)) = (x^2)(x-7) = x^3 -7x^2
then (goh)(5) = (5^3)-7(5)^2 = 124-7(25) = 124-175 = -51
Answer is -1/3
you would divide both sides by 18 to get the variable on its own and that would leave you with -6/18 and so you have to simplify it by dividing the numerator and denominator by the greatest common factor (6) to get your remaining simplified fraction of -1/3