There is no simple answer. Sometimes, the nature of one of the equations lends itself to the substitution method but at other times, elimination is better. If they are non-linear equations, and there is an easy substitution then that is the best approach. With linear equations, using the inverse matrix is the fastest method.
If you mean: y = 6x-4 and y = 7x-7 then by substitution x = 3 and y = 14
Substitution is a way to solve without graphing, and sometimes there are equations that are impossible or very difficult to graph that are easier to just substitute. Mostly though, it is a way to solve if you have no calculator or cannot use one (for a test or worksheet).
True. To solve a three variable system of equations you can use a combination of the elimination and substitution methods.
If it has infinite number of solutions that means that any ordered pair put into the system will make it true. I believe the relationship of the graphs question your asking is that tooth equations will probably be the same line
Plug your ordered pair into both of your equations to see if you get they work.
The first step is to show the equations which have not been shown.
As there is no system of equations shown, there are zero solutions.