First, it gives you y=-3x-4 for the first equation so you can plug in -3x-4 into the second equation for y. Then you get -6x-2(-3x-4)=-5. When you distribute the -2, you get -6x+6x+8=-5. The 6x and -6x cancel out so then you have 8=-5. This is never true meaning that there are no solutions and the lines are parallel.
