a + b - 2c = -6 2a - 5b + c = -4 -3a - 7b - 3c = -13

a+b-2c=-6. (1)
2a-5b+c=-4. (2)
-3a-7b-3c=-13 (3)
*pers 1 dan 2
a + b - 2c = -6|x2|2a + 2b - 4c = -12
2a-5b + c = -4|x1|2a - 5b + c. = -4 ±
7b - 5c = -8.....(4)
*pers 1 dan 3
a + b - 2c = -6 |x3|3a + 3b -6c = -18
-3a-7b-3c= -13|x1|-3a - 7b -3c = -13 ±
-4b - 9c = -31..(5)
* 4 ke pers 5
7b - 5c = -8 |x9|63b - 45c = -72
-4b - 9c= -31|x5|-20b -45c = -155 _
83b = 83
b = 1
substitusi b=1 ke pers 4
7b - 5c = -8
7.1 - 5c= -8
-5c = -8 -7
-5c = -15
c = 3
substitusi b=1 dan c=3 ke pers 1
a +b - 2c = -6
a + 1 - 2.3= -6
a + 1 - 6 = -6
a - 5 = -6
a = -6 + 5
a = -1