Реши примеры: a) 4 2/21 * 10 - 19 20/21

a) $4\frac{2}{21} \cdot 10 - 19\frac{20}{21} = \frac{86}{21} \cdot 10 - \frac{419}{21} = \frac{860}{21} - \frac{419}{21} = \frac{441}{21} = 21$ б) $24\frac{8}{41} : 4 - 18\frac{5}{41} : 3 = \frac{1000}{41} : 4 - \frac{743}{41} : 3 = \frac{250}{41} - \frac{743}{123} = \frac{750 - 743}{123} = \frac{7}{123}$ в) $3\frac{5}{4} : 6 + 2\frac{1}{2} - 1 \frac{1}{5} : 1\frac{1}{9} = \frac{17}{4} : 6 + \frac{5}{2} - \frac{6}{5} : \frac{10}{9} = \frac{17}{24} + \frac{5}{2} - \frac{6}{5} \cdot \frac{9}{10} = \frac{17}{24} + \frac{5}{2} - \frac{54}{50} = \frac{17}{24} + \frac{5}{2} - \frac{27}{25} = \frac{425 + 1500 - 648}{600} = \frac{1277}{600} = 2 \frac{77}{600}$ г) $7\frac{1}{2} : 2\frac{2}{3} - 12\frac{1}{4} : 3 + 2\frac{3}{8} = \frac{15}{2} : \frac{8}{3} - \frac{49}{4} : 3 + \frac{19}{8} = \frac{15}{2} \cdot \frac{3}{8} - \frac{49}{4} \cdot \frac{1}{3} + \frac{19}{8} = \frac{45}{16} - \frac{49}{12} + \frac{19}{8} = \frac{135 - 196 + 114}{48} = \frac{53}{48} = 1\frac{5}{48}$