Jika x dan y penyelesaian Sari sistem persamaan 5x-2y=9 2x+3y=-4. Maka nilai x-3y adalah

5x - 2y = 9
2x + 3y = -4
eliminasi x
5x - 2y = 9   | *2 | 10x - 4y = 18
2x + 3y = -4 | *5 | 10x+15y= -20
                             ------------------  -
                                     -19y = 38
                                          y = 38 / -19
                                          y = -2
subtitusi nilai y = -2 ke persamaan 2x +3y = -4
<----> 2x + 3(-2) = -4
           2x - 6 = -4
                2x = -4 + 6
                2x = 2
                  x =2 /2 = 1
nilai x-3y = 1-3(-2)
               = 1+6
               = 7