You can use GeoGebra to solve systems of equations.                                                                                                                                                                                                                                          
     GeoGebra Instruction 1
CAS CAS     under         View     in         Menu.         CAS,         pressing         Enter     to         start         a         new         row         for         each         of         your         equations.         Shift     key,         click         the         box         of         the         first         equation         and         then         click         the         box         with         the         row         number         of         the         last         equation.         Solve      If you get  as the output, the system of equations has no solution. If GeoGebra returns one of the variables as a function, the system of equations has infinitely many solutions. 
      
You can solve a system of equations graphically by plotting all the graphs in the same coordinate system. The solutions are intersections between the graphs.
     GeoGebra Instruction 2
Graphics View Algebra     View     and         Graphics     View     under         View     in         Menu.         CAS,         pressing         Enter     to         start         a         new         row         for         each.         Toolbar,         click         Intersect Toolbar     for         Graphics     View     by         clicking         on         any         empty         space         inside         the         Graphics     View     window.         Then         find         the         button         under         the         Point Graphics     View.         The         order         does         not         matter.         Algebra     View     as         coordinates         of         the         intersection         points.