\(a)\dfrac{5}{77}-\dfrac{-4}{7}=\dfrac{5}{77}+\dfrac{44}{77}=\dfrac{49}{77}=\dfrac{7}{11}\\b)\dfrac{4}{33}-\dfrac{6}{-11}=\dfrac{4}{33}+\dfrac{18}{33}=\dfrac{22}{33}=\dfrac{2}{3} \\c)\dfrac{25}{7}-\dfrac{61}{21}=\dfrac{75}{21}-\dfrac{61}{21}=\dfrac{14}{21}=\dfrac{2}{3} \\d)\dfrac{5}{10}-\dfrac{1}{2}=\dfrac{1}{2}-\dfrac{1}{2}=0\)
\(e)\dfrac{2}{3}-\dfrac{-5}{6}=\dfrac{4}{6}+\dfrac{5}{6}=\dfrac{9}{6}=\dfrac{3}{2} \\f)\dfrac{5}{6}-\dfrac{-1}{3}=\dfrac{5}{6}+\dfrac{2}{6}=\dfrac{7}{6}\)