Enumeration of equations in the double dollar math mode

First, do not use double dollars for display mathematics. I teach freshman math students to use LaTeX for all homeworks and projects during sophomore-senior years and they are taught not to use double dollars for display mathematics for two of many reasons. 1) It is no longer considered the correct (current) way to delineate display mathematics 2) If is not in line with 'best practices' as there are a number of situations where they do not work correctly (or as expected)

Second to answer the question which should have been: "How do I number equations delineated by \[...\] ?" I searched this site for 'numbering equations' and found this reference: Giving an equation between \[ \]'s a number