are the pros and cons of each of the above three methods? Which method do you
prefer or like best? And why is that?
Each can be good and an "best-fit" for a particular problem and/or situation. Limited in time and scratch paper space? Elimination or substitution may be shortest. But to gain a visual insight and see it tangibly at work in the real world, nothing beats graphing - what we draw tends to have much more mental "stiuckiness" than more abstract methods... (only my gut-level opinion :-)