\[Страница\ 63.\]
\[\boxed{\mathbf{2.}}\]
\[\textbf{а)}\frac{5}{9} \cdot 18 = \frac{5 \cdot 18}{9} = \frac{5 \cdot 2}{1} = 10\]
\[\textbf{б)}\frac{2}{5} \cdot 14 = \frac{2 \cdot 14}{5} = \frac{28}{5} = 5\frac{3}{5}\]
\[\textbf{в)}\frac{3}{8} \cdot 20 = \frac{3 \cdot 20}{8} = \frac{3 \cdot 5}{2} = 7\frac{1}{2}\]
\[\textbf{г)}\frac{6}{7} \cdot 5 = \frac{6 \cdot 5}{7} = \frac{30}{7} = 4\frac{2}{7}\]
\[\textbf{д)}\ 16 \cdot \frac{1}{8} = \frac{16 \cdot 1}{8} = 2\]
\[\textbf{е)}\ 15 \cdot \frac{7}{25} = \frac{15 \cdot 7}{25} = \frac{3 \cdot 7}{5} =\]
\[= \frac{21}{5} = 4\frac{1}{5}\]
\[\textbf{ж)}\ 21 \cdot \frac{5}{14} = \frac{21 \cdot 5}{14} = \frac{15}{2} = 7\frac{1}{2}\]
\[\textbf{з)}\ 26 \cdot \frac{7}{13} = \frac{26 \cdot 7}{13} = 14\]
\[\boxed{\mathbf{3.}}\]
\[\textbf{а)}\frac{3}{4} \cdot \frac{1}{5} = \frac{3}{20};\ \ \ \ \ \]
\[\frac{9}{11} \cdot \frac{11}{27} = \frac{1}{3};\ \ \ \]
\[\frac{3}{5} \cdot \frac{20}{15} = \frac{4}{5};\ \ \ \ \ \]
\[\frac{26}{49} \cdot \frac{7}{13} = \frac{2}{7}\]
\[\textbf{б)}\frac{5}{7} \cdot \frac{1}{2} = \frac{5}{14};\ \ \ \ \ \]
\[\frac{5}{7} \cdot 0 = 0;\ \ \ \ \ \]
\[\frac{2}{7} \cdot \frac{14}{19} = \frac{4}{19};\ \ \ \ \ \]
\[\frac{17}{18} \cdot \frac{4}{17} = \frac{2}{9}\]
\[\textbf{в)}\ \frac{5}{9} \cdot \frac{3}{10} = \frac{1}{6};\ \ \ \ \ \]
\[1 \cdot \frac{8}{19} = \frac{8}{19};\ \ \ \ \]
\[\frac{8}{25} \cdot \frac{5}{16} = \frac{1}{10};\ \ \ \ \ \ \ \ \]
\[\frac{14}{45} \cdot \frac{50}{21} = \frac{20}{27}\]
\[\textbf{г)}\ \frac{3}{5} \cdot \frac{10}{21} = \frac{2}{7};\ \ \ \ \ \]
\[\frac{7}{26} \cdot \frac{2}{3} = \frac{7}{39};\ \ \ \ \]
\[\frac{13}{11} \cdot \frac{11}{13} = 1;\ \ \ \ \]
\[\frac{36}{49} \cdot \frac{7}{12} = \frac{3}{7}\]