$$\begin{array}{l} {\text{Известно}}{\text{, что}} \hfill \\ \left\{ \begin{gathered} {c^3} - 3{c^2} + 5c - 17 = 0 \hfill \\ {d^3} - 3{d^2} + 5d + 11 = 0 \hfill \\ \end{gathered} \right.. \hfill \\ {\text{Найдите }}c + d. \hfill \\ \end{array} $$