X+y+z=42 X+y=20 X+z=10

Eliminasi
X + Y + Z = 42
X + Y = 20 -
----------------------
Z= 22

Masukkan nilai Z (22)
X + Z = 20
X + 22 = 20
X = 20 - 22
X = -2

cari nilai Y
X + Y + Z = 42
-2 + Y + 22 = 42
Y + 20 = 42
Y = 42 - 20
Y = 22