Show that the planes `2x-y+6z=5` and `5x-2.5y+15z=12` are parallel.

Explanation

The given planes are in the form `a_(1)x+b_(1)y+c_(1)z+d_(1)=0` and `a_(2)x+b_(2)y+c_(2)z+d_(2)=0`, where `a_(1)/a_(2)=b_(1)/b_(2)=c_(1)/c_(2)`. Hence, the given planes are parallel.