Answer
Neither,
$cos^{-1}|\dfrac{-1}{\sqrt {11}}| \approx 95.2 ^{\circ}$
Work Step by Step
$n_1=\lt1,-1,3\gt$ and $n_2=\lt 3,1,-1\gt$
Angle between two vectors$\theta= cos^{-1}|\dfrac{a.b}{|a||b|}|$
$\theta= cos^{-1}|\dfrac{-1}{\sqrt {11} \sqrt {11}}|$
$\theta= cos^{-1}|\dfrac{-1}{\sqrt {11}}|$
$\theta \approx 95.2 ^{\circ}$
Hence, the two planes are neither parallel or perpendicular.