well, again, if we were to solve for "y" on each and put them in slope-intercept form, we'd get
as you can see, they have the same slope, meaning the lines are parallel to each other, however the y-intercept is different, so these are two parallel lines with a gap in between, and parallel lines with a gap never touch each other, thus no intersections and thus no solutions.
This is correct because to find the perpendicular, you need to find the opposite reciprocal of the slope. In this case, the slope is 4/7, so the opposite reciprocal is -7/4.