5 21 9 — : — = 7 15 24 4 8 20 — : — = 5 10 2 6 3 28 — : — = 7 9 30 40 20 3 — : — = 50 5 4 17 10 5 — : — = 20 34 2 15 150 2 — : — = 20 200 3 14 18 2 — : — = 63 28 6 77 11 65 — : — = 25 13 7 81 2 18 — : — = 90 3 20 42 7 3 — : — = 60 12 21

Выполним действия с дробями:

1. $$\frac{5}{7} : \frac{21}{15} : \frac{9}{24} = \frac{5}{7} \cdot \frac{15}{21} \cdot \frac{24}{9} = \frac{5 \cdot 15 \cdot 24}{7 \cdot 21 \cdot 9} = \frac{1800}{1323} = \frac{200}{147}$$
2. $$\frac{4}{5} : \frac{8}{10} : \frac{2}{2} = \frac{4}{5} \cdot \frac{10}{8} \cdot \frac{2}{2} = \frac{4 \cdot 10 \cdot 2}{5 \cdot 8 \cdot 2} = \frac{80}{80} = 1$$
3. $$\frac{6}{7} : \frac{3}{9} : \frac{28}{30} = \frac{6}{7} \cdot \frac{9}{3} \cdot \frac{30}{28} = \frac{6 \cdot 9 \cdot 30}{7 \cdot 3 \cdot 28} = \frac{1620}{588} = \frac{135}{49}$$
4. $$\frac{40}{50} : \frac{20}{5} : \frac{3}{4} = \frac{40}{50} \cdot \frac{5}{20} \cdot \frac{4}{3} = \frac{40 \cdot 5 \cdot 4}{50 \cdot 20 \cdot 3} = \frac{800}{3000} = \frac{2}{15}$$
5. $$\frac{17}{20} : \frac{10}{34} : \frac{5}{2} = \frac{17}{20} \cdot \frac{34}{10} \cdot \frac{2}{5} = \frac{17 \cdot 34 \cdot 2}{20 \cdot 10 \cdot 5} = \frac{1156}{1000} = \frac{289}{250}$$
6. $$\frac{15}{20} : \frac{150}{200} : \frac{2}{3} = \frac{15}{20} \cdot \frac{200}{150} \cdot \frac{3}{2} = \frac{15 \cdot 200 \cdot 3}{20 \cdot 150 \cdot 2} = \frac{9000}{6000} = \frac{3}{2} = 1\frac{1}{2}$$
7. $$\frac{14}{63} : \frac{18}{28} : \frac{2}{6} = \frac{14}{63} \cdot \frac{28}{18} \cdot \frac{6}{2} = \frac{14 \cdot 28 \cdot 6}{63 \cdot 18 \cdot 2} = \frac{2352}{2268} = \frac{4}{3} = 1\frac{1}{3}$$
8. $$\frac{77}{25} : \frac{11}{13} : \frac{65}{7} = \frac{77}{25} \cdot \frac{13}{11} \cdot \frac{7}{65} = \frac{77 \cdot 13 \cdot 7}{25 \cdot 11 \cdot 65} = \frac{7007}{17875} = \frac{49}{125}$$
9. $$\frac{81}{90} : \frac{2}{3} : \frac{18}{20} = \frac{81}{90} \cdot \frac{3}{2} \cdot \frac{20}{18} = \frac{81 \cdot 3 \cdot 20}{90 \cdot 2 \cdot 18} = \frac{4860}{3240} = \frac{3}{2} = 1\frac{1}{2}$$
10. $$\frac{42}{60} : \frac{7}{12} : \frac{3}{21} = \frac{42}{60} \cdot \frac{12}{7} \cdot \frac{21}{3} = \frac{42 \cdot 12 \cdot 21}{60 \cdot 7 \cdot 3} = \frac{10584}{1260} = \frac{84}{10} = 8\frac{4}{10} = 8\frac{2}{5}$$

Ответ: Выше приведены решения.