bantu nomor 4 dong :)

Matriks

z = 8 + (-5) = 3

x - 3y = -13 ... (1)
2x + 5y = -4 ... (2)

Eliminasi substitusi
persamaan (1) kalikan 2

2x - 6y = -26
2x + 5y = -4
------------------- (-)
-11y = -22
y = 2

x - 3y = -13
x = -13 + 3y
x = -7

••
x - y - z = -7 - 2 - 3 = -12 ✔