-> (x³ + y³ + z³ - 3xyz)
= (x + y + z) (x² + y² + z² - xy - yz - zx)
= (x + y + z) [(x + y + z)² - 3(xy + yz + zx)]
= 9 x (81 - 3 x 23)
= (9 x 12)
= 108