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Решите задачу:

$\frac{7}{8} * \frac{10}{21} = \frac{7:7}{8:2} * \frac{10:2}{21:7}=\frac{1}{4} * \frac{5}{3}= \frac{5}{12}$

$\frac{12}{5} * \frac{9}{16} * \frac{35}{27} =\frac{12:4}{5:5} * \frac{9:9}{16:4} * \frac{35:5}{27:9} = \frac{3*1*7}{1*4*3} = \frac{21}{12} =1 \frac{9}{12}=1 \frac{3}{4}$

$8* \frac{3}{4} = \frac{8:4}{1} * \frac{3}{4:4} = \frac{2*3}{1*1} =6$

$3 \frac{3}{5} *1 \frac{1}{9} = \frac{18}{5} * \frac{10}{9} = \frac{18:9}{5:5} * \frac{10:5}{9:9} = \frac{2*2}{1*1} = \frac{4}{1} =4$