If I am asked to solve a systems of equation, how would I know which method (substitution, or elimination) to use? What set of conditions should I be looking for, or is it that either method should in theory work?
Then say that I am given the following system of equation, but neither substituion nor elimination produces the correct result (based on what I have did thus far)
$xy = 4$
$2x - y - 7 = 0$
How would I go on about solving this type of one?