I've tried my best with the MathJax thing but it's my first time using it!
V = $\mathbb{C}[x]_{90}$ is the $\mathbb{C}$-vector space consisting of all polynomials of degree $\leq$ 90. $D:V\to V$ is the linear map given by
$D(f) = \frac{d^3f}{dx^3}$,
find $ch_D(x)$ & $m_D(x)$ (characteristic and minimal polynomials)
B={ $\frac{x^n}{n!}$|0$\leq$ n $\leq$ 90} is a basis for V
Divide B into a series of sets $B_i$ such that $B_1 \cup ...\cup B_i$ is a basis for the generalized eigenspaces $V_i(0)$, and show that D($B_i) \subset B_{i-1}$, so that B is a Jordan basis for B. Hence find the Jordan normal form of D.
I think that $ch_D(x)$ & $m_D(x)$ both are $x^{91}$? I have no idea at all how to continue though! Any help would be appreciated.