Помоги мне решить номера 21-25

Конечно, сейчас помогу! 21. а) $\frac{9}{10} \cdot \frac{5}{12} = \frac{3 \cdot 3 \cdot 5}{2 \cdot 5 \cdot 3 \cdot 4} = \frac{3}{2 \cdot 4} = \frac{3}{8}$ б) $\frac{3}{5} \cdot \frac{11}{5} = \frac{33}{25} = 1 \frac{8}{25}$ в) $\frac{21}{22} : \frac{2}{5} = \frac{21}{22} \cdot \frac{5}{2} = \frac{21 \cdot 5}{22 \cdot 2} = \frac{105}{44} = 2 \frac{17}{44}$ г) $\frac{7}{8} : \frac{7}{16} = \frac{7}{8} \cdot \frac{16}{7} = \frac{7 \cdot 2 \cdot 8}{8 \cdot 7} = 2$ д) $1\frac{3}{5} : 2\frac{1}{2} = \frac{8}{5} : \frac{5}{2} = \frac{8}{5} \cdot \frac{2}{5} = \frac{16}{25}$ е) $1\frac{3}{4} : 10\frac{1}{2} = \frac{7}{4} : \frac{21}{2} = \frac{7}{4} \cdot \frac{2}{21} = \frac{7 \cdot 2}{2 \cdot 2 \cdot 3 \cdot 7} = \frac{1}{6}$ 22. а) $\frac{8}{9} : 6 = \frac{8}{9} \cdot \frac{1}{6} = \frac{2 \cdot 4}{9 \cdot 2 \cdot 3} = \frac{4}{27}$ б) $15 : \frac{5}{6} = 15 \cdot \frac{6}{5} = \frac{3 \cdot 5 \cdot 6}{5} = 3 \cdot 6 = 18$ в) $1 : \frac{3}{7} = 1 \cdot \frac{7}{3} = \frac{7}{3} = 2\frac{1}{3}$ г) $\frac{2}{5} : 12 = \frac{2}{5} \cdot \frac{1}{12} = \frac{2}{5 \cdot 2 \cdot 6} = \frac{1}{30}$ д) $2\frac{7}{9} : 15 = \frac{25}{9} : 15 = \frac{25}{9} \cdot \frac{1}{15} = \frac{5 \cdot 5}{9 \cdot 3 \cdot 5} = \frac{5}{27}$ е) $3\frac{1}{3} : 30 = \frac{10}{3} : 30 = \frac{10}{3} \cdot \frac{1}{30} = \frac{10}{3 \cdot 3 \cdot 10} = \frac{1}{9}$ 23. a) $10:3 = \frac{10}{3} = 3\frac{1}{3}$ б) $42:8 = \frac{42}{8} = \frac{21}{4} = 5\frac{1}{4}$ в) $57:30 = \frac{57}{30} = \frac{19}{10} = 1\frac{9}{10}$ г) $28:42 = \frac{28}{42} = \frac{2 \cdot 14}{3 \cdot 14} = \frac{2}{3}$ 24. а) $25 \cdot (\frac{7}{10} + \frac{3}{5} + \frac{1}{2}) = 25 \cdot (\frac{7}{10} + \frac{6}{10} + \frac{5}{10}) = 25 \cdot \frac{18}{10} = \frac{5 \cdot 5 \cdot 18}{2 \cdot 5} = \frac{5 \cdot 18}{2} = 5 \cdot 9 = 45$ б) $5 : 1\frac{1}{4} + 7 : 1\frac{1}{3} = 5 : \frac{5}{4} + 7 : \frac{4}{3} = 5 \cdot \frac{4}{5} + 7 \cdot \frac{3}{4} = 4 + \frac{21}{4} = \frac{16}{4} + \frac{21}{4} = \frac{37}{4} = 9\frac{1}{4}$ 25. а) $6\frac{6}{11} : 2\frac{3}{4} : 2\frac{2}{5} \cdot 2\frac{1}{5} = \frac{72}{11} : \frac{11}{4} : \frac{12}{5} \cdot \frac{11}{5} = \frac{72}{11} \cdot \frac{4}{11} \cdot \frac{5}{12} \cdot \frac{11}{5} = \frac{72 \cdot 4 \cdot 5 \cdot 11}{11 \cdot 11 \cdot 12 \cdot 5} = \frac{12 \cdot 6 \cdot 4 \cdot 5 \cdot 11}{11 \cdot 11 \cdot 12 \cdot 5} = \frac{6 \cdot 4}{11} = \frac{24}{11} = 2\frac{2}{11}$ б) $9\frac{1}{3} : \frac{7}{8} : \frac{7}{16} : \frac{14}{27} = \frac{28}{3} : \frac{7}{8} : \frac{7}{16} : \frac{14}{27} = \frac{28}{3} \cdot \frac{8}{7} \cdot \frac{16}{7} \cdot \frac{27}{14} = \frac{4 \cdot 7 \cdot 8 \cdot 16 \cdot 27}{3 \cdot 7 \cdot 7 \cdot 2 \cdot 7} = \frac{4 \cdot 8 \cdot 16 \cdot 9}{7 \cdot 7} = \frac{36864}{49} = 752\frac{16}{49}$ в) $(\frac{5}{14} + \frac{18}{35}) + (\frac{1}{4} - \frac{5}{14}) : (\frac{5}{12})^2 = (\frac{25}{70} + \frac{36}{70}) + (\frac{7}{28} - \frac{10}{28}) : \frac{25}{144} = \frac{61}{70} + (-\frac{3}{28}) : \frac{25}{144} = \frac{61}{70} - \frac{3}{28} \cdot \frac{144}{25} = \frac{61}{70} - \frac{3 \cdot 36}{7 \cdot 25} = \frac{61}{70} - \frac{108}{175} = \frac{305}{350} - \frac{216}{350} = \frac{89}{350}$ г) $(\frac{7}{12} - \frac{8}{15}) \cdot 2\frac{4}{5} + \frac{4}{35} \cdot (\frac{7}{10} - \frac{9}{16}) = (\frac{35}{60} - \frac{32}{60}) \cdot \frac{14}{5} + \frac{4}{35} \cdot (\frac{56}{80} - \frac{45}{80}) = \frac{3}{60} \cdot \frac{14}{5} + \frac{4}{35} \cdot \frac{11}{80} = \frac{1}{20} \cdot \frac{14}{5} + \frac{4}{35} \cdot \frac{11}{80} = \frac{7}{50} + \frac{11}{700} = \frac{98}{700} + \frac{11}{700} = \frac{109}{700}