X+y=9 2y+3z=7 x-2z=4 Maka x-y+z…

X + y = 9
x – 2z = 4
——————- —
y + 2z = 5
——————- × 2
2y + 4z = 10
2y + 3z = 7
——————- —
>>>>> z = 3

x – 2z = 4
x = 4 + 2z
x = 4 + 2(3)
x = 4 + 6
x = 10

x + y = 9
y = 9 – x
y = 9 – 10
y = -1

Jadi, x – y + z = 10-(-1)+3 = 10+1+3 = 14