[tex]a)\\\\\frac{2}{3}+\frac{6}{7}=\frac{14}{21}+\frac{18}{21}=\frac{32}{21}=1\frac{11}{21}\\\\\\\frac{7}{8}+\frac{5}{6}=\frac{21}{24}+\frac{20}{24}= \frac{41}{24}=1\frac{17}{24}\\\\\\b)\\\\5\frac{1}{4}+\frac{5}{6}=5\frac{3}{12}+\frac{10}{12}=5\frac{13}{12}=6\frac{1}{12}[/tex]
[tex]1\frac{7}{9}+2\frac{3}{10}= 1\frac{70}{90}+2\frac{27}{90}=3\frac{97}{90}=4\frac{7}{90}\\\\\\2\frac{7}{8}+3\frac{1}{6}=2\frac{21}{24}+3\frac{4}{24}= 5\frac{25}{24}=6\frac{1}{24}\\\\c)\\\\\frac{8}{9}-\frac{2}{5}=\frac{40}{45}-\frac{18}{45}=\frac{22}{45}\\\\\\\frac{7}{8}-\frac{4}{5}=\frac{35}{40}-\frac{32}{40}=\frac{3}{40}[/tex]
[tex]4\frac{5}{6}-\frac{1}{4}=4\frac{10}{12}-\frac{3}{12}=4\frac{7}{10} \\\\d)\\\\6\frac{8}{9}-1\frac{1}{2}=6\frac{16}{18}-1\frac{9}{18} =5\frac{7}{18}\\\\\\8\frac{5}{7}-3\frac{2}{5}=8\frac{25}{35}-3\frac{14}{35}=5\frac{11}{35}\\\\\\4\frac{1}{4}-4\frac{1}{6}=4\frac{3}{12}-4\frac{2}{12}=1\frac{1}{12}[/tex]
