\[\boxed{\text{5.358.}}\]
\[\textbf{а)}\ \frac{7 \cdot 4}{14 \cdot 3} = \frac{7 \cdot 2 \cdot 2}{2 \cdot 7 \cdot 3} =\]
\[\textbf{б)}\ \frac{2 \cdot 9}{9 \cdot 10} = \frac{2}{10} = \frac{1}{5}\]
\[\textbf{в)}\ \frac{9 \cdot 7 \cdot 13}{7 \cdot 13 \cdot 18} = \frac{9}{18} = \frac{1}{2}\]