Dengan cara sibstitusi x+2y=9 -5x+2y=27

x+2y = 9 => x = 9-2y.
-5x+2y = 27 .
-5 ( 9-2y) +2y = 27 .
-45+10y+2y = 27 .
12y = 27+45 .
y = 72 : 12 .
y = 6 .
x = 9-2y .
x = 9-2 ( 6 ) .
x = 9-12 .
x = -3 .