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3/10 + ((17/20 - 5/6 - 2/3)/(- 3/2 - 5)^2 + 8/13 - 4/5)^3·((1/7 + 3/4)/(- 1/2 + 3/7))=

=3/10 + ((- 13/20)/(- 13/2)^2 + 8/13 - 4/5)^3·(25/28/(- 1/14))=

=3/10 + ((- 13/20)/(169/4) + 8/13 - 4/5)^3·(- 25/2)=

=3/10 + (- 1/65 + 8/13 - 4/5)^3·(- 25/2)=

=3/10 + (- 1/5)^3·(- 25/2)=

=3/10 + (- 1/125)·(- 25/2)=

=3/10 + 1/10 = 2/5

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$\small \dfrac{3}{10}+\left[\left(\dfrac{17}{20}-\dfrac{5}{6}-\dfrac{2}{3}\right) : \left(-\dfrac{3}{2}-5\right)^2+\dfrac{8}{13}-\dfrac{4}{5}\right]^3·\left[\left(\dfrac{1}{7}+\dfrac{3}{4}\right) : \left(-\dfrac{1}{2}+\dfrac{3}{7}\right)\right] =$

$\small =\dfrac{3}{10}+\left[\left(\dfrac{51-50-40}{60}\right) : \left(\dfrac{-3-10}{2}\right)^2+\dfrac{8}{13}-\dfrac{4}{5}\right]^3·\left[\left(\dfrac{4+21}{28}\right) : \left(\dfrac{-7+6}{14}\right)\right] =$

$\small =\dfrac{3}{10}+\left[-\dfrac{\cancel{39}^{13}}{\cancel{60}_{20}} : \left(-\dfrac{13}{2}\right)^2+\dfrac{8}{13}-\dfrac{4}{5}\right]^3·\left[\dfrac{25}{28} : -\dfrac{1}{14}\right] =$

$\small =\dfrac{3}{10}+\left[-\dfrac{13}{20} : \dfrac{169}{4}+\dfrac{8}{13}-\dfrac{4}{5}\right]^3·\left[\dfrac{25}{\cancel{28}_2} · -\dfrac{\cancel{14}^1}{1}\right] =$

$\small =\dfrac{3}{10}+\left[-\dfrac{\cancel{13}^1}{\cancel{20}_5} · \dfrac{\cancel4^1}{\cancel{169}_{13}}+\dfrac{8}{13}-\dfrac{4}{5}\right]^3·\left[\dfrac{25}{2} · -\dfrac{1}{1}\right] =$

$\small =\dfrac{3}{10}+\left[-\dfrac{1}{5} · \dfrac{1}{13}+\dfrac{8}{13}-\dfrac{4}{5}\right]^3·-\dfrac{25}{2} =$

$\small =\dfrac{3}{10}+\left[-\dfrac{1}{65} +\dfrac{8}{13}-\dfrac{4}{5}\right]^3·-\dfrac{25}{2} =$

$\small =\dfrac{3}{10}+\left[\dfrac{-1+40-52}{65}\right]^3·-\dfrac{25}{2} =$

$\small =\dfrac{3}{10}+\left[-\dfrac{\cancel{13}^1}{\cancel{65}_5}\right]^3·-\dfrac{25}{2} =$

$\small =\dfrac{3}{10}+\left[-\dfrac{1}{5}\right]^3·-\dfrac{25}{2} =$

$\small =\dfrac{3}{10}-\dfrac{1}{\cancel{125}_5}·-\dfrac{\cancel{25}^1}{2} =$

$\small =\dfrac{3}{10}-\dfrac{1}{5}·-\dfrac{1}{2} =$

$\small =\dfrac{3}{10}+\dfrac{1}{10} =$

$\small =\dfrac{\cancel4^2}{\cancel{10}_5} = \dfrac{2}{5}$

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