If we seperate the items inside the parenthesis:
$$ ( -1 \cdot 8 \cdot x \cdot x)^{\frac{2}{3}} $$
We can take care of the 2 exponent first by doubling the terms inside the parenthesis.
$$ ( -1 \cdot 8 \cdot x \cdot x)^{\colorbox{aqua}{$2$}\cdot \frac{1}{3}} $$
$$ ( -1 \cdot -1 \cdot 8 \cdot 8 \cdot x \cdot x \cdot x \cdot x)^{\frac{1}{3}} $$
The negative values cancel each other out. The current exponent is equivalent to a cube root.
$$ \sqrt[3]{8\cdot 8\cdot x\cdot x \cdot x \cdot x} $$
We can take out a \(x\) since there are three of them, but we should obtain the prime factors of \(8\) to see if anything else can be simplified.
$$ \sqrt[3]{\colorbox{aqua}{$2 \cdot 2 \cdot 2$} \cdot \colorbox{aqua}{$2 \cdot 2 \cdot 2$} \cdot \colorbox{aqua}{$x \cdot x \cdot x$} \cdot x} $$
$$ = 2\cdot 2\cdot x \cdot \sqrt[3]{x} $$
$$ = 4x \sqrt[3]{x} $$