Question

Three equation starting with x=4

Answer 1

I don't know what you mean, but I can tell you that it is a vertical line and has no slope (or no defined slope) it's slope is UNDEFINED.

Go 4 units right from the origin and you fill find (0,4), sketch a vertical line from there. This is the graph of x=4.

Answer 2

i agree not enough information and one minor correction to what @Solomon posted
that should be
(x,y) (4,0)