a)
[tex]\frac{5}{6}-\frac{3}{4}=\frac{10}{12}-\frac{9}{12}=\frac{1}{12}\\\\\frac{3}{4}-\frac{2}{9}=\frac{27}{36}-\frac{8}{36}=\frac{19}{36}[/tex]
b)
[tex]1\frac{1}{2}-\frac{2}{5}=1\frac{5}{10}-\frac{4}{10}=1\frac{1}{10}\\\\2\frac{5}{8}-1\frac{1}{4}=2\frac{5}{8}-1\frac{2}{8}=1\frac{3}{8}\\\\3\frac{3}{4}-1\frac{1}{6}=3\frac{9}{12}-1\frac{2}{12}=2\frac{7}{12}[/tex]
c)
[tex]1\frac{1}{5}-\frac{1}{2}=1\frac{2}{10}-\frac{5}{10}=\frac{12}{10}-\frac{5}{10}=\frac{7}{10}\\\\1\frac{1}{4}-\frac{3}{5}=1\frac{5}{20}-\frac{12}{20}=\frac{25}{20}-\frac{12}{20}=\frac{13}{20}\\\\2\frac{2}{3}-\frac{3}{4}=2\frac{8}{12}-\frac{9}{12}=1\frac{20}{12}-\frac{9}{12}=1\frac{11}{12}[/tex]
