\[1)\ За\ 2\ часа:\]
\[a = 360{^\circ} \bullet \frac{1}{12} \bullet 2 = 60{^\circ}.\]
\[Ответ:\ \ 60{^\circ}.\]
\[2)\ За\ 5\ часов:\]
\[a = 360{^\circ} \bullet \frac{1}{12} \bullet 5 = 150{^\circ}.\]
\[Ответ:\ \ 150{^\circ}.\]
\[3)\ За\ 8\ часов:\]
\[a = 360{^\circ} \bullet \frac{1}{12} \bullet 8 = 240{^\circ}.\]
\[Ответ:\ \ 240{^\circ}.\]
\[4)\ За\ 30\ минут:\]
\[a = 360{^\circ} \bullet \frac{1}{12} \bullet \frac{30}{60} = 15{^\circ}.\]
\[Ответ:\ \ 15{^\circ}.\]
\[5)\ За\ 12\ часов:\]
\[a = 360{^\circ} \bullet \frac{1}{12} \bullet 12 = 360{^\circ}.\]
\[Ответ:\ \ 360{^\circ}.\]