mohon bantuannya kak

4x - 3y + 2z = 40 |×7
5x + 9y - 7z = 47 |×2
maka
28x - 21y + 14z = 280
10x + 18y - 14z = 94
------------------------------(+)
38x - 3y = 374

4x - 3y + 2z = 40 |×3
9x + 8y - 3z = 97 |×2
maka
12x - 9y + 6z = 120
18x + 16y - 6z = 194
----------------------------(+)
30x + 7y = 314

38x - 3y = 374 |×7
30x + 7y = 314 |×3
maka
266x - 21y = 2618
90x + 21y = 942
-------------------------(+)
356x = 3560
x = 10

38x - 3y = 374
38(10) - 3y = 374
380 - 3y = 374
- 3y = 374 - 380
- 3y = - 6
y = 2

4x - 3y + 2z = 40
4(10) - 3(2) + 2z = 40
40 - 6 + 2z = 40
34 + 2z = 40
2z = 40 - 34
2z = 6
z = 3

nilai x : y + z
= 10 : 2 + 3
= 5 + 3
= 8 ( E )