Tentukan nilai x - 2y = ... Dari persamaan: 2x + y = 10 y - z = 2 2z + x = 7

2x + y = 10
y = 10 - 2x

y - z = 2
z = y - 2

2z + x = 7
2(y-2) + x = 7
2y - 4 + x = 7
x = 11 - 2y
x = 11 - 2(10 - 2x)
x = 11 - 20 + 4x
3x = 9
x = 3

y = 10 - 2x = 10 - 2(3)
y = 4


Jadi,

nilai dari x - 2y = 3 - 2(4) = -5