$a) \dfrac{0,375-0,3+\dfrac{3}{11}+\dfrac{3}{12}}{-0,625+0,5-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{1,5+1-0,75}{2,5+\dfrac{5}{3}-1,25}\\=\dfrac{\dfrac{3}{8}-\dfrac{3}{10}+\dfrac{3}{11}+\dfrac{3}{12}}{-\dfrac{5}{8}+\dfrac{1}{2}-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{1,75}{1,25+\dfrac{5}{3}}\\=\dfrac{\dfrac{263}{440}}{-\dfrac{263}{264}}+\dfrac{\frac{7}{4}}{\dfrac{5}{3}+\dfrac{5}{3}}\\=-\dfrac{\dfrac{263}{440}}{\dfrac{263}{264}}+\dfrac{\frac{7}{4}}{\dfrac{35}{12}}\\=-\dfrac{3}{5}+\dfrac{3}{5}=0\\b) \dfrac{\frac{1}{3}-\dfrac{1}{7}-\dfrac{1}{13}}{\dfrac{2}{3}-\dfrac{2}{7}-\dfrac{2}{13}}.\dfrac{\dfrac{1}{3}-0,25+0,2}{1\dfrac{1}{6}-0,875+0,7}+\dfrac{6}{7}\\=\dfrac{\dfrac{31}{273}}{\dfrac{62}{273}}.\dfrac{\frac{1}{3}-0,05}{\dfrac{7}{6}-0,875+0,7}+\dfrac{6}{7}\\=\dfrac{31}{62}.\dfrac{\frac{1}{3}-\dfrac{1}{20}}{\dfrac{7}{6}-0,175}+\dfrac{6}{7}\\=\dfrac{1}{2}.\dfrac{\dfrac{17}{60}}{\dfrac{7}{6}-\dfrac{7}{40}}+\dfrac{6}{7}\\=\dfrac{1}{2}.\dfrac{\frac{17}{60}}{\dfrac{119}{120}}+\dfrac{6}{7}\\=\dfrac{1}{2}.\dfrac{2}{7}+\dfrac{6}{7}\\=\dfrac{1}{7}+\dfrac{6}{7}=1$
