a) (6-3\frac{5}{12})-(3-1\frac{1}{12}); б) (5-2\frac{7}{19})-(4-3\frac{2}{19}); в) (7-3\frac{7}{11})-(4-2\frac{3}{11}); г) (8-4\frac{13}{20}) - (6-5\frac{3}{20}).

a) $$(6-3\frac{5}{12})-(3-1\frac{1}{12})=6-3\frac{5}{12}-3+1\frac{1}{12}=6-3-3-\frac{5}{12}+1\frac{1}{12}=0+\frac{12+1}{12}-\frac{5}{12}=\frac{13}{12}-\frac{5}{12}=\frac{13-5}{12}=\frac{8}{12}=\frac{2}{3}$$

б) $$(5-2\frac{7}{19})-(4-3\frac{2}{19})=5-2\frac{7}{19}-4+3\frac{2}{19}=5-4-2\frac{7}{19}+3\frac{2}{19}=1+3\frac{2}{19}-2\frac{7}{19}=1+3-2+\frac{2}{19}-\frac{7}{19}=2+\frac{2}{19}-\frac{7}{19}=2+\frac{2-7}{19}=2-\frac{5}{19}=1\frac{19-5}{19}=1\frac{14}{19}$$

в) $$(7-3\frac{7}{11})-(4-2\frac{3}{11})=7-3\frac{7}{11}-4+2\frac{3}{11}=7-4-3\frac{7}{11}+2\frac{3}{11}=3-3\frac{7}{11}+2\frac{3}{11}=3+2-3+\frac{3}{11}-\frac{7}{11}=2+\frac{3}{11}-\frac{7}{11}=2+\frac{3-7}{11}=2-\frac{4}{11}=1\frac{11-4}{11}=1\frac{7}{11}$$

г) $$(8-4\frac{13}{20}) - (6-5\frac{3}{20})=8-4\frac{13}{20}-6+5\frac{3}{20}=8-6-4\frac{13}{20}+5\frac{3}{20}=2-4\frac{13}{20}+5\frac{3}{20}=2+5-4+\frac{3}{20}-\frac{13}{20}=3+\frac{3}{20}-\frac{13}{20}=3+\frac{3-13}{20}=3-\frac{10}{20}=3-\frac{1}{2}=2\frac{2-1}{2}=2\frac{1}{2}$$

Ответ: а) $$\frac{2}{3}$$, б) $$1\frac{14}{19}$$, в) $$1\frac{7}{11}$$, г) $$2\frac{1}{2}$$