1) To find out we need to calculate the dot product of those two vectors
[tex]\begin{gathered} m\cdot n=\mleft\langle1,5\mright\rangle\cdot\mleft\langle3,15\mright\rangle=1\cdot3+5\cdot15=3+75=78 \\ \end{gathered}[/tex]Since these vectors have a dot product different than zero, then they are not Orthogonal.
2) Let's now check if they are perpendicular, calculating the norm of each one and the angle between them:
[tex]\begin{gathered} \mleft\|m\mright\|=\sqrt[]{1^2+5^2}=\sqrt[]{26} \\ \|n\|=\sqrt[]{3^2+15^2}=\sqrt[]{9+225}=\sqrt[]{234} \end{gathered}[/tex]And finally the angle theta between them:
[tex]\begin{gathered} \theta=\cos ^{-1}(\frac{u\cdot v}{\|m\|\cdot\|n\|}) \\ \theta=\cos ^{-1}(\frac{78}{\sqrt[]{26}\cdot\sqrt[]{234}}) \\ \theta=0 \end{gathered}[/tex]3) Since the angle is 0, these vectors are parallel since parallel vectors for 0º or 180º
