Question 283359
You solve this by substituting x^2 into the expansion of x^5.
{{{x^2=3x+4}}}
{{{x^5=x*x^2*x^2}}}
   ---> {{{x^5=x(3x+4)(3x+4)}}}
    {{{x^5=(3x^2+4x)(3x+4)=9x^3+24x^2+16x=9x*(3x+4)+24(3x+4)+16x=27x^2+36x+72x+96+16x=27x^2+124x+96=27(3x+4)+124x+96=81x+108+124x+96=205x+204}}}

D is indeed the answer, but I hope you now see how to do it.