5x+2y=10, 2y=-5x+10, y=-2.5x+5
15x+4y=-4, 4y=-15x-4, y=-3.75x-1
-2.5 != -3.75
And -2.5m=-1, m=0.4, 0.4 !=-3.75
So the slopes are not equal and they are also not negative reciprocals of one another.
Thus the lines are neither parallel nor perpendicular.
