a) $A = \dfrac{3}{2} + \dfrac{7}{6} + \dfrac{13}{12} + \dfrac{21}{20} + \dfrac{31}{30} + \dfrac{43}{42} + \dfrac{57}{56} + \dfrac{73}{72} + \dfrac{91}{90}$
$A = 1 + \dfrac{1}{2} + 1 + \dfrac{1}{6} + 1 + \dfrac{1}{12} + 1 + \dfrac{1}{20} + 1 + \dfrac{1}{30} + 1 + \dfrac{1}{42} + 1 + \dfrac{1}{56} + 1 + \dfrac{1}{72} + 1 + \dfrac{1}{90}$
$A = (1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1) + \left ( \dfrac{1}{2} + \dfrac{1}{6} + \dfrac{1}{12} + \dfrac{1}{20} + \dfrac{1}{30} + \dfrac{1}{42} + \dfrac{1}{56} + \dfrac{1}{72} + \dfrac{1}{90} \right )$
$A = 9 + \left ( \dfrac{1}{2} + \dfrac{1}{6} + \dfrac{1}{12} + \dfrac{1}{20} + \dfrac{1}{30} + \dfrac{1}{42} + \dfrac{1}{56} + \dfrac{1}{72} + \dfrac{1}{90} \right )$
$A = 9 + \left ( \dfrac{1}{1.2} + \dfrac{1}{2.3} + \dfrac{1}{3.4} + \dfrac{1}{4.5} + \dfrac{1}{5.6} + \dfrac{1}{6.7} + \dfrac{1}{7.8} + \dfrac{1}{8.9} + \dfrac{1}{9.10} \right )$
$A = 9 + \left ( 1 - \dfrac{1}{2} + \dfrac{1}{2} - \dfrac{1}{3} + \dfrac{1}{3} - \dfrac{1}{4} + \dfrac{1}{4} - \dfrac{1}{5} + \dfrac{1}{5} - \dfrac{1}{6} + \dfrac{1}{6} - \dfrac{1}{7} + \dfrac{1}{7} - \dfrac{1}{8} + \dfrac{1}{8} - \dfrac{1}{9} + \dfrac{1}{9} - \dfrac{1}{10} \right )$
$A = 9 + \left ( 1 - \dfrac{1}{10} \right )$
$A = 9 + \dfrac{9}{10}$
$A = \dfrac{99}{10}$
b) $B = \dfrac{0,75 - 0,6 + \dfrac{3}{7} + \dfrac{3}{13}}{2,75 - 2,2 + \dfrac{11}{7} + \dfrac{11}{13}} : \dfrac{0,6 - \dfrac{1}{3} + \dfrac{3}{11}}{1,4 - \dfrac{7}{9} + \dfrac{7}{11}}$
$B = \dfrac{\dfrac{3}{4} - \dfrac{3}{5} + \dfrac{3}{7} + \dfrac{3}{13}}{\dfrac{11}{4} - \dfrac{11}{5} + \dfrac{11}{7} + \dfrac{11}{13}} : \dfrac{\dfrac{3}{5} - \dfrac{3}{9} + \dfrac{3}{11}}{\dfrac{7}{5} - \dfrac{7}{9} + \dfrac{7}{11}}$
$B = \dfrac{\dfrac{3}{4} - \dfrac{3}{5} + \dfrac{3}{7} + \dfrac{3}{13}}{\dfrac{11}{4} - \dfrac{11}{5} + \dfrac{11}{7} + \dfrac{11}{13}} : \dfrac{\dfrac{3}{5} - \dfrac{3}{9} + \dfrac{3}{11}}{\dfrac{7}{5} - \dfrac{7}{9} + \dfrac{7}{11}}$
$B = \dfrac{3.\left ( \dfrac{1}{4} - \dfrac{1}{5} + \dfrac{1}{7} + \dfrac{1}{13} \right )}{11.\left ( \dfrac{1}{4} - \dfrac{1}{5} + \dfrac{1}{7} + \dfrac{1}{13} \right )} : \dfrac{3.\left ( \dfrac{1}{5} - \dfrac{5}{9} + \dfrac{1}{11} \right )}{7.\left ( \dfrac{1}{5} - \dfrac{5}{9} + \dfrac{1}{11} \right )}$
$B = \dfrac{3}{11} : \dfrac{3}{7}$
$B = \dfrac{7}{11}$
