Answer
$5 x \sqrt[3] 3$
Work Step by Step
$6\sqrt[3] (24x^{3}) - 2\sqrt[3] (81x^{3}) - x\sqrt[3] 3 $
$= 6\sqrt[3] (3 \times 8 \times x^{3}) - 2\sqrt[3] (3 \times 27 \times x^{3}) - x\sqrt[3] 3 $
$= 6\sqrt[3] (3 \times 2^{3} \times x^{3}) - 2\sqrt[3] (3 \times 3^{3} \times x^{3}) - x\sqrt[3] 3 $
$= 6 \times 2 \times x \sqrt[3] 3 - 2 \times 3 \times x \sqrt[3] 3 - x\sqrt[3] 3 $
$=12x \sqrt[3] 3 -6x \sqrt[3] 3 - x\sqrt[3] 3 $
$=5 x \sqrt[3] 3$