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-(2/5-1/2)-[1/10-3/5-(3/2-17/10)]=

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$-\bigg(\dfrac{2}{5}-\dfrac{1}{2}\bigg)-\bigg[\dfrac{1}{10}-\dfrac{3}{5}-\bigg(\dfrac{3}{2}-\dfrac{17}{10}\bigg)\bigg]=$

$=-\bigg(\dfrac{4-5}{10}\bigg)-\bigg[\dfrac{1}{10}-\dfrac{3}{5}-\bigg(\dfrac{15-17}{10}\bigg)\bigg]=$

$=-\bigg(-\dfrac{1}{10}\bigg)-\bigg[\dfrac{1}{10}-\dfrac{3}{5}-\bigg(-\dfrac{\cancel2^1}{\cancel{10}_5}\bigg)\bigg]=$

$=\dfrac{1}{10}-\bigg[\dfrac{1}{10}-\dfrac{3}{5}-\bigg(-\dfrac{1}{5}\bigg)\bigg]=$

$=\dfrac{1}{10}-\bigg[\dfrac{1}{10}-\dfrac{3}{5}+\dfrac{1}{5}\bigg]=$

$=\dfrac{1}{10}-\bigg[\dfrac{1-6+2}{10}\bigg]=$

$=\dfrac{1}{10}-\bigg[-\dfrac{3}{10}\bigg]=$

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

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

$=\dfrac{2}{5}$