\[\boxed{\text{5.462.}}\]
\[\textbf{а)}\ \frac{2}{3}\ ч \cdot 6 = 2\ ч \cdot 2 = 4\ ч.\]
\[\textbf{б)}\ \frac{7}{12}\ ч \cdot 8 = \frac{7 \cdot 8}{12}\ ч = \frac{14}{3}\ ч =\]
\[= 4\frac{2}{3}\ ч.\]
\[\textbf{в)}\ \frac{5}{24}\ ч \cdot 24 = 5\ ч.\]
\[\textbf{г)}\ \frac{7}{15}\ ч \cdot 10 = \frac{7 \cdot 10}{15}\ ч = \frac{14}{3}\ ч =\]
\[= 4\frac{2}{3}\ ч.\]
\[\textbf{д)}\ \frac{5}{6}\ ч \cdot 12 = 5\ ч \cdot 2 = 10\ ч.\]