1: =2/3+5/7+2/3=4/3+5/7
=28/21+15/21=43/21
2: \(=\dfrac{1}{5}\left(\dfrac{4}{7}-\dfrac{3}{7}-1\right)=\dfrac{1}{5}\cdot\dfrac{-6}{7}=\dfrac{-6}{35}\)
3: =-3/5(-1/9-5/6+7/2)
=-3/5(-2/18-15/18+63/18)
=-3/5*46/18
=-3/5*23/9
=-69/45=-23/15
4: \(=\dfrac{5}{13}+\dfrac{8}{13}-\dfrac{20}{41}-\dfrac{21}{41}-\dfrac{5}{7}=\dfrac{-5}{7}\)
5: \(=\dfrac{6}{7}\left(\dfrac{8}{13}+\dfrac{9}{13}-\dfrac{3}{13}\right)=\dfrac{6}{7}\cdot\dfrac{14}{13}=\dfrac{12}{13}\)
6: \(=\dfrac{-3}{7}\left(\dfrac{15}{13}-\dfrac{11}{13}-1\right)=\dfrac{-3}{7}\cdot\dfrac{-9}{13}=\dfrac{27}{91}\)
7: \(=\dfrac{3}{8}-\dfrac{7}{9}-\dfrac{2}{9}-\dfrac{5}{8}+\dfrac{5}{9}=\dfrac{-1}{4}-1+\dfrac{5}{9}\)
=5/9-5/4
=-25/36
8: \(=\dfrac{1}{2}\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{11}-\dfrac{1}{13}\right)=\dfrac{1}{2}\cdot\dfrac{10}{39}=\dfrac{5}{39}\)
9: \(=12\cdot\dfrac{14-8+87}{12}=101-8=93\)
