Systems of Linear Equations

Which of the following choices of a will result in a system of linear equations with exactly one solution?

So, dead ass, I'm bad at systems of linear equations, so this might not be difficult for somebody else but I had trouble. But I'll explain it.

So you have to put the equations into slope intercept form. As long as the slopes of the two equations are different, then they will have exactly one equation. If they have the same slope, then they can either have no solutions or infinite solutions. In this case, the a is independent from the x and thus has no effect on the slope. Therefore, the value of a can be anything.