We are given two non-parallel planes which intersect to produce a line.
I assume the planes are:
x-2y+4z=0, x+4z=2y, 3x+12z=6y,
3x-2y+5z=0, 3x+5z=2y.
12z-5z=4y, 7z=4y, z=4y/7; x=2y-4z=2y-16y/7=-2y/7.
Now we have x and z in terms of y. Let y=t so that we can parameterise the line:
x=-2t/7, y=t, z=4t/7.
Therefore t=-7x/2=y=7z/4 and the parameterised equations is: -7x/2=y=7z/4.
Without fractions: -14x=4y=7z.