subtract 4x from each side first. 8x-4x+60=4x-4x+100 which equals 4x+60=100. Then subtract 60 from each side. 4x+60-60=100-60 which equals 4x=40. Then divide both side by 4 which equals x=10.
All I know is they can’t be parallel because they don’t have the same gradient. I don’t think they are perpendicular either but don’t fully trust me on that