Question

What is the solution to `2x=4` and `y=-3` when graphing?

Answer 1

It is actually two lines meeting at a point!
The first equation `2x=4` is the equation of a vertical line passing through `x=4/2=2` while the second is the equation of a horizontal line passing through `y=-3`.
They both meet at the point `P` of coordinates: `(2,-3)`
Graphically:

(It is basically what you normally do to plot a point on the Cartesian Plane)