[tex]\dfrac{4}{5} +\dfrac{2}{5} =\dfrac{6}{5} =\boxed{1\dfrac{1}{5} }[/tex]
[tex]4\dfrac{2}{7} +1\dfrac{2}{7} =\boxed{5\dfrac{4}{7} }[/tex]
[tex]3\dfrac{4}{5} +1\dfrac{3}{4} =3\dfrac{16}{20} +1\dfrac{15}{20} =4\dfrac{31}{20} =\boxed{5\dfrac{11}{20} }[/tex]
[tex]5\dfrac{3}{4} +4\dfrac{7}{8} =5\dfrac{6}{8} +4\dfrac{7}{8} =9\dfrac{13}{8} =\boxed{10\dfrac{5}{8} }[/tex]
[tex]4\dfrac{1}{5} -1\dfrac{2}{3} =4\dfrac{3}{15} -1\dfrac{10}{15} =3\dfrac{18}{15} -1\dfrac{10}{15} =\boxed{2\dfrac{8}{15} }[/tex]
[tex]5\dfrac{2}{3} -3\dfrac{1}{4} =5\dfrac{8}{12} -3\dfrac{3}{12} =\boxed{2\dfrac{5}{12} }[/tex]
[tex]10\dfrac{6}{7} -2\dfrac{4}{21} =10\dfrac{18}{21} -2\dfrac{4}{21} =8\dfrac{14}{21}=\boxed{8\dfrac{2}{3} }[/tex]
[tex]12\dfrac{1}{5}- 2\dfrac{4}{9} =12\dfrac{9}{45} -2\dfrac{20}{45} =11\dfrac{54}{45} -2\dfrac{20}{45} =\boxed{9\dfrac{34}{45} }[/tex]
