mohon bantuannya ya.. diketahui x - 2y = 5; 2x + 3z = 12; y + 2z = 3. nilai x + y+ z =

x - 2y = 5 ..................(1)
2x + 3z = 12 .............(2)
y + 2z = 3 .................(3)

x - 2y = 5 ..................(1)
x = 5 + 2y .................(4)

Selanjutnya, subtitusi persamaan (4) ke (2)
2x + 3z = 12 ..............(2)
2(5 + 2y) + 3z = 12
10 + 4y + 3z = 12
4y + 3z = 2 ...............(5)

Elimimasi persamaan (5) dan (3)
4y + 3z = 2 ..............(×2)
y + 2z = 3 ................(×3)

8y + 6z = 4
3y + 6z = 9
------------------ -
5y = -5
y = -1

Subtitusi y = -1 ke persamaan (4)
x = 5 + 2y
x = 5 + 2(-1)
x = 3

Subtitusi y = -1 ke persamaan (3)
y + 2z = 3
(-1) + 2z = 3
2z = 4
z = 2

x = 3
y = -1
z = 2

Maka nilai dari :
x + y + z = 3 + (-1) + 2
x + y + z = 4


Semoga membantu :)