Representing constraints with equations and inequalities isn't the easiest thing in the world, but these activities should make these ideas easier for students to understand by showing how they can be used in all sorts of different contexts.

We start with the basics. Graphed inequalities differ from equations, since the former have those shaded areas, so we start by just focusing on that visual aspect of systems of inequalities. "Bob the Builder" allows students to set up constraints using a system of inequalities, making a tidy little picture without being bogged down in too many abstractions.