Aiuto

249)

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$\left(-\dfrac{7}{12}+\dfrac{3}{5}-\dfrac{1}{6}\right)-\left(-\dfrac{3}{4}+\dfrac{8}{5}-\dfrac{3}{2}\right)+\left(-\dfrac{11}{15}-\dfrac{7}{4}+1+\dfrac{3}{20}\right)=$

$=\left(\dfrac{-35+36-10}{60}\right)-\left(\dfrac{-15+32-30}{20}\right)+\left(\dfrac{-44-105+60+9}{60}\right)=$

$=\left(-\dfrac{9}{60}\right)-\left(-\dfrac{13}{20}\right)+\left(-\dfrac{80}{60}\right)=$

$=\left(-\dfrac{\cancel9^3}{\cancel{60}_{20}}\right)+\dfrac{13}{20}+\left(-\dfrac{\cancel{80}^4}{\cancel{60}_3}\right)=$

$=\left(-\dfrac{3}{20}\right)+\dfrac{13}{20}+\left(-\dfrac{4}{3}\right)=$

$=\dfrac{10}{20}-\dfrac{4}{3}=$

$=\dfrac{\cancel{10}^1}{\cancel{20}_2}-\dfrac{4}{3}=$

$=\dfrac{1}{2}-\dfrac{4}{3}=$

$=\dfrac{3-8}{6}=$

$=-\dfrac{5}{6}$