selesaikanlah menggunakan metode substitusi, eliminasi, grafik, dan campuran -x+3y=0 x+3y=12

-x + 3y = 0
x + 3y = 12
------------------ -
2x = -12
x = -12/2
x = -6

substitusi x = -6 ke x + 3y = 12
x + 3y = 12
-6 + 3y = 12
3y = 12 + 6
3y = 18
y = 18/3
y = 6