Answer
$111.3^\circ$.
Work Step by Step
From what we learned: $\cos\theta=\frac{U\cdot V}{|U||V|}=\frac{13\cdot2+(-8)\cdot11}{\sqrt{13^2+(-8)^2}\sqrt{2^2+11^2}}=\frac{-62}{\sqrt{235}\cdot\sqrt{125}}=\frac{-62}{\sqrt{29375}}$
Thus $\theta=\cos^{-1}\frac{-62}{\sqrt{29375}}\approx111.3^\circ$.