Answer
80.1 km, 25.9$^{\circ}$ south of west
Work Step by Step
Let $x$ = length of highway
$x = \sqrt (72.0^{2} + 35.0^{2}) = \sqrt 6409 \approx 80.1\; km $
$tan(\theta) = \frac{35.0}{72.0}$
$\theta\approx25.9^{\circ}$ south of west (or north of east)
