$(3\frac{4}{9} - 1\frac{16}{21}) : 1\frac{11}{42} - 1\frac{5}{7} : 6 = 1\frac{1}{21}$
а) $3\frac{4}{9} - 1\frac{16}{21} = 3\frac{28}{63} - 1\frac{48}{63} = 2\frac{91}{63} - 1\frac{48}{63} = 1\frac{43}{63}$
б) $1\frac{43}{63} : 1\frac{11}{42} = \frac{106}{63} : \frac{53}{42} = \frac{106}{63} * \frac{42}{53} = \frac{2}{3} * \frac{2}{1} = \frac{4}{3} = 1\frac{1}{3}$
в) $1\frac{5}{7} : 6 = \frac{12}{7} * \frac{1}{6} = \frac{2}{7} * \frac{1}{1} = \frac{2}{7}$
г) $1\frac{1}{3} - \frac{2}{7} = 1\frac{7}{21} - \frac{6}{21} = 1\frac{1}{21}$

$(4\frac{2}{3} : 3\frac{1}{2} - 3\frac{1}{2} : 4\frac{2}{3}) : 1\frac{17}{18} = \frac{3}{10}$
а) $4\frac{2}{3} : 3\frac{1}{2} = \frac{14}{3} : \frac{7}{2} = \frac{14}{3} * \frac{2}{7} = \frac{2}{3} * \frac{2}{1} = \frac{4}{3} = 1\frac{1}{3}$
б) $3\frac{1}{2} : 4\frac{2}{3} = \frac{7}{2} : \frac{14}{3} = \frac{7}{2} * \frac{3}{14} = \frac{1}{2} * \frac{3}{2} = \frac{3}{4}$
в) $1\frac{1}{3} - \frac{3}{4} = 1\frac{4}{12} - \frac{9}{12} = \frac{16}{12} - \frac{9}{12} = \frac{7}{12}$
г) $\frac{7}{12} : 1\frac{17}{18} = \frac{7}{12} : \frac{35}{18} = \frac{7}{12} * \frac{18}{35} = \frac{1}{2} * \frac{3}{5} = \frac{3}{10}$