д) $$ \frac{5}{12} + \frac{1}{6}$$; e) $$ \frac{3}{5} - \frac{4}{15}$$; ж) $$ \frac{19}{21} - \frac{11}{15}$$; з) $$ \frac{5}{42} + \frac{10}{63}$$; и) $$ \frac{11}{21} + \frac{2}{26}$$; к) $$ \frac{5}{24} - \frac{7}{60}$$

Выполним действия с дробями: д) $$ \frac{5}{12} + \frac{1}{6} = \frac{5}{12} + \frac{1 \cdot 2}{6 \cdot 2} = \frac{5}{12} + \frac{2}{12} = \frac{5+2}{12} = \frac{7}{12} $$ е) $$ \frac{3}{5} - \frac{4}{15} = \frac{3 \cdot 3}{5 \cdot 3} - \frac{4}{15} = \frac{9}{15} - \frac{4}{15} = \frac{9-4}{15} = \frac{5}{15} = \frac{1}{3} $$ ж) $$ \frac{19}{21} - \frac{11}{15} = \frac{19 \cdot 5}{21 \cdot 5} - \frac{11 \cdot 7}{15 \cdot 7} = \frac{95}{105} - \frac{77}{105} = \frac{95-77}{105} = \frac{18}{105} = \frac{6}{35} $$ з) $$ \frac{5}{42} + \frac{10}{63} = \frac{5 \cdot 3}{42 \cdot 3} + \frac{10 \cdot 2}{63 \cdot 2} = \frac{15}{126} + \frac{20}{126} = \frac{15+20}{126} = \frac{35}{126} = \frac{5}{18} $$ и) $$ \frac{11}{21} + \frac{2}{26} = \frac{11 \cdot 26}{21 \cdot 26} + \frac{2 \cdot 21}{26 \cdot 21} = \frac{286}{546} + \frac{42}{546} = \frac{286+42}{546} = \frac{328}{546} = \frac{164}{273} $$ к) $$ \frac{5}{24} - \frac{7}{60} = \frac{5 \cdot 5}{24 \cdot 5} - \frac{7 \cdot 2}{60 \cdot 2} = \frac{25}{120} - \frac{14}{120} = \frac{25-14}{120} = \frac{11}{120} $$