if the plane is in the form then the normal vector is
We also know that two planes are parallel iff their normal vectors are parallel.
So the two normal vectors are and these two vectors are parallel (the second is 2 times the first)
so the planes are parallel since their normal vectors are parallel.
The planes are distinct becuase they are not multiples of each other.
For the second I would use the Dot Product
the angle between two vectors is
the normals are
doing some computations
plugging into above we get
so the angle is
P.s I think that 13.5 is a better answer