Answer:
guess and check
Explanation:
Linear equation systems usually have two or more variables to find.
The values for these variables can be found by different methods, some of them are indeed graphing, substitution and with matrices.
So these are correct options that are used to solve linear systems of equations.
On the other hand, the guess and check method is not used to find the solution of these systems, since the more variables the system has the more difficult it is to guess the answer, the graphic and mathematical methods are more effective and reliable.