jika 3x-y=15 dan x+3y =3,maka hasil dari x-2y=.........

3x-y = 15......(1
x+3y = 3
x = 3-3y........(2

substitusi pers. (2 ke pers. (1
3(3-3y)-y = 15
9-9y-y = 15
-10y = 6
y = -6/10
y = -3/5

x = 3-3y
x = 3-3(-3/5)
x = 3+(9/5)
x = (15+9)/5
x = 24/5
x = 4 4/5

x-2y
= (24/5)- 2(-3/5)
=(24/5)+(6/5)
= 30/5
=6