Please solve this..

10. Simplify $\left[\left\{{\left(\frac{-2}{5}\right)}^{-7}\times {\left(\frac{-2}{5}\right)}^9\right\}+{\left(\frac{-2}{5}\right)}^2\right]$ and express the result as a 
11. Simplify:
(i) $\left[{\left(-\frac{1}{3}\right)}^8÷{\left(-\frac{1}{3}\right)}^5\right]-\left[{\left(\frac{-1}{3}\right)}^5÷{\left(\frac{-1}{3}\right)}^3\right]$
(iii) $\frac{1}{1+a^{n-m}}+\frac{1}{1+a^{m-n}}$

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