3.4․18 Tangents and normals

condition: \[ \begin{array}{lrr} \text { Find } \quad \text { angle } & \text { between } & \text { lines } \\ \left\{\begin{array}{c} 2 x-y+z-4=0 \\ 3 x+2 y-z-6=0 \end{array}\right. & \text { and } & \frac{x+2}{-1}=\frac{y+4}{-7}=\frac{z-5}{-5} . \end{array}\]