\(a,=\left(-\dfrac{3}{5}+\dfrac{4}{9}-\dfrac{2}{5}+\dfrac{5}{9}\right):\dfrac{7}{11}=\left(-1+1\right):\dfrac{7}{11}=0:\dfrac{7}{11}=0\\ b,=\dfrac{6}{7}:\left(\dfrac{3}{26}-\dfrac{3}{13}+\dfrac{1}{10}-\dfrac{8}{5}\right)=\dfrac{6}{7}:\left(\dfrac{3.6}{26}+\dfrac{1-8.2}{10}\right)=\dfrac{6}{7}:\left(\dfrac{-3}{26}+-\dfrac{3}{2}\right)=\dfrac{6}{7}:\left(-\dfrac{21}{13}\right)=-\dfrac{49}{26}\\ c,=\left(\dfrac{1.2-9}{10}\right):\left(-\dfrac{13}{9}\right)-\left(\dfrac{1}{5}+\dfrac{8}{5}\right):\dfrac{5}{4}=\left(-\dfrac{7}{10}\right):\left(-\dfrac{13}{9}\right)-\dfrac{9}{5}:\dfrac{5}{4}=\dfrac{63}{130}-\dfrac{36}{25}=-\dfrac{621}{650}\)
