5/7 * 21/15 : 9/24 =

1) $\frac{5}{7} \cdot \frac{21}{15} \div \frac{9}{24} = \frac{5}{7} \cdot \frac{21}{15} \cdot \frac{24}{9} = \frac{1 \cdot 3 \cdot 24}{1 \cdot 3 \cdot 9} = \frac{24}{9} = \frac{8}{3} = 2\frac{2}{3}$ 2) $\frac{4}{5} \div \frac{8}{10} \div \frac{20}{2} = \frac{4}{5} \cdot \frac{10}{8} \cdot \frac{2}{20} = \frac{4 \cdot 10 \cdot 2}{5 \cdot 8 \cdot 20} = \frac{80}{800} = \frac{1}{10}$ 3) $\frac{6}{7} \cdot \frac{3}{9} \cdot \frac{28}{30} = \frac{6 \cdot 3 \cdot 28}{7 \cdot 9 \cdot 30} = \frac{1 \cdot 1 \cdot 4}{1 \cdot 3 \cdot 5} = \frac{4}{15}$ 4) $\frac{40}{50} \div \frac{20}{5} \cdot \frac{3}{4} = \frac{4}{5} \cdot \frac{5}{20} \cdot \frac{3}{4} = \frac{4 \cdot 5 \cdot 3}{5 \cdot 20 \cdot 4} = \frac{3}{20}$ 5) $\frac{17}{20} \div \frac{10}{34} \div \frac{5}{2} = \frac{17}{20} \cdot \frac{34}{10} \cdot \frac{2}{5} = \frac{17 \cdot 34 \cdot 2}{20 \cdot 10 \cdot 5} = \frac{1156}{1000} = 1,156 = \frac{289}{250} = 1\frac{39}{250}$ 6) $\frac{15}{20} \div \frac{150}{200} \div \frac{2}{3} = \frac{3}{4} \div \frac{3}{4} \div \frac{2}{3} = \frac{3}{4} \cdot \frac{4}{3} \cdot \frac{3}{2} = \frac{3}{2} = 1\frac{1}{2}$ 7) $\frac{14}{63} \cdot \frac{18}{28} \cdot \frac{2}{6} = \frac{2}{9} \cdot \frac{9}{14} \cdot \frac{1}{3} = \frac{2 \cdot 9 \cdot 1}{9 \cdot 14 \cdot 3} = \frac{1}{21}$ 8) $\frac{77}{25} \div \frac{11}{13} \cdot \frac{65}{7} = \frac{77}{25} \cdot \frac{13}{11} \cdot \frac{65}{7} = \frac{7 \cdot 13 \cdot 13}{1 \cdot 5} = \frac{1183}{5} = 236,6 = 236\frac{3}{5}$ 9) $\frac{81}{90} \cdot \frac{2}{3} \div \frac{18}{20} = \frac{9}{10} \cdot \frac{2}{3} \cdot \frac{20}{18} = \frac{3 \cdot 2 \cdot 20}{10 \cdot 3 \cdot 2} = \frac{2}{3} = 2\frac{2}{3}$ (Опечатка в примере: $81/90 = 9/10$, $9/10*2/3 = 18/30 = 3/5$, $3/5 * 20/18 = 60/90 = 2/3$. Результат: $2/3$) 10) $\frac{42}{60} \div \frac{7}{12} \div \frac{3}{21} = \frac{42}{60} \cdot \frac{12}{7} \cdot \frac{21}{3} = \frac{6 \cdot 12 \cdot 7}{60 \cdot 1} = \frac{504}{60} = 8,4 = 8\frac{2}{5}$