\[x{^\circ} - \angle B;2x{^\circ} - \angle A;6x{^\circ} - \angle C.\]
\[x + 2x + 6x = 180\]
\[9x = 180\ \ \ \]
\[x = 20{^\circ}\ \ \ \ \]
\[2 \bullet 20 = 40{^\circ}\ \ \ \ \]
\[6 \bullet 20 = 120{^\circ}\]
\[Ответ:\angle A = 40{^\circ};\ \angle B = 20{^\circ};\ \]
\[\angle C = 120{^\circ}.\]