Hi,

First look at what is inside the parentheses, which I assume is $\left( 27^r \right)^{-1}.$ This can be written $\frac{1}{27^r}.$ Hence your expression can be written

\[\left( \frac{1}{27^r} \right)^\frac{-2}{3}.\]

The negative sign in the exponent tells me that $\left( \frac{1}{27^r} \right)$ should be inverted and hence the expression can now be written

\[\left( 27^r \right)^\frac{2}{3}.\]

But $27 = 3^3$ so make this substitution and simplify.

I hope this helps,
Penny