x - y + 2z =5 2x + y -z =9 x - 2y + 3x = 4

X - y + 2z =5........(1)
2x + y -z =9.........(2)
x - 2y + 3x = 4......(3)

jawab:            x - y + 2z =5
                      x - 2y + 3z = 4
                     --------------------(-)
                                 y - z = 1.........(4)


x - y + 2z =5    (x2)      2x-2y +4z = 10
2x + y -z =9     (x1)      2x + y - z  = 9
                                    --------------------(-)
                                  -3y + 5z = 1.......(5)

y - z = 1         (x3)      3y - 3z = 3
-3y+5z=1       (x1)     -3y + 5z= 1
                                 -----------------(+)
                                         2z = 4
                                           z = 2

y - z = 1
y - 2 = 1
     y = 3

x - y + 2z = 5
x - 3 + 2(2) = 5
x - 3 + 4 = 5
     x + 1  = 5
           x  = 4

jadi, x =4
        y= 3
        z=2