The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 14.2418\\[1 em]x_2 &= 1.8791+1.3949i\\[1 em]x_3 &= 1.8791-1.3949i \end{aligned} $$Polynomial $ x^3-18x^2+59x-78 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.