tolonggyaaaa, pakai caraa

eliminasi 1&2
2x + 3y + 4z = 2 | × 1
x - 2y + z = 5 | × 2
= 2x+3y+4z=2
2x-4y+2z=10
= 7y + 2z = -8 (4)

eliminasi 3&4
y+2z=4
7y+2z = -8
= 6y=12
y = 2

* y + 2z=4
(2) + 2z =4
2z= 2
z = 1
* x + 3y + 4z = 5
x + 3(2) + 4(1) = 5
x + 6 + 4 = 5
x = 5-10
x = -5

* x + y + z =?
(-5)+(2)+(1)
= -2