I couldn’t find any Khan Academy lesson on this. The basic idea: instead of having just one inequality (in two dimensions) we have a SYSTEM of linear inequalities.  This  means that there will be more than one.  Graph and shade the first inequality, then graph and shade the second inequality. If the problem is an “and” problem then both sets must be true and the solution set is the overlap. If the problem  is an “or” problem then either set or the overlap must be true. This will mean there will be three shaded regions.