Jika 8x - 7z = 12, 5x + 2y = 17 dan 6y - 4z = 8 maka.. A. x < z B. y = z C. x = y + z D. z = x - y E. y > z

Mencari nilai z
8x - 7z = 12
8x = 12 + 7z
x = (12 + 7z)/8 ... (1)

5x + 2y = 17
5x = 17 - 2y
x = (17 - 2y)/5 ... (2)

6y - 4z = 8
6y = 8 + 4z
y = 8/6 + 4z/6 ... (3)

Substitusi (3) ke (2)
x = 17/5 - 2y/5
   = 17/5 - 2(8/6 + 4z/6)/5
   = 17/5 - (16+8z)/30
   = 17/5 - 16/30 - 8z/30
   = 86/30 - 8z/30
   = (43-4z)/15 ... (4)

Substitusi (4) ke (1)
(43-4z)/15 = (12+7z)/8
8(43-4z) = 15(12+7z)
344-32z = 180 + 105z
137z = 164
z = 164/137

Mencari nilai x (dari persamaan (1))
x = (12+7z)/8 = (12 + 7(164/137))/8 = 349/137

Mencari nilai y (dari persamaan (3))
y = (8+4z)/6 = (8+4(164/137))/6 = 292/137


x = 349/137, y = 292/137 dan z = 164/137
Dari hasil tersebut, maka y > z