I know that raising a power to another power means multiplying the exponents, so $(7^{-1})^{-1} = 7^{(-1)(-1)}$. Multiplying two negative numbers gives a positive result, so $(-1)(-1) = 1$. Therefore, $7^{(-1)(-1)} = 7^1 = 7$. So $(7^{-1})^{-1} = 7$. 
What is $(7^{-1})^{-1}$?