Solve: $2x+5y=8, -10x-7y=-4$ or $x+2y=3, 4x+5y=6$ you will find that they have the same solutions. In fact any two simultaneous equations of the form: $ax+(a+d)y=a+2d, bx+(b+e)y=b+2e$ will have the same solution.
I thought this was interesting and wondered if the result can be generalised. I think in 3d, 3 planes will share a line of solutions.