Geometric interpretation
The whole of the solutions of an inequation (linear) corresponds to a half space in RN (a half-plane in R2).
The whole of the solutions of an equation (linear) corresponds to a hyperplan in RN (a line in R2).
The whole of the solutions of a system of equations and inequations (linear) corresponds to the intersection of the half spaces and the hyperplans associated with each element with the system.
This intersection, called acceptable field, is convex and defines a polyhedron in RN (a polygonal area in R2).