\[Рисунок\ в\ учебнике.\]
\[\angle AOC = \angle ABC + 25{^\circ}:\]
\[\angle AOC = \cup AC = 2\angle ABC;\]
\[\angle ABC + 25{^\circ} = 2\angle ABC;\]
\[\angle ABC = 25{^\circ};\]
\[\angle AOC = 2 \bullet 25{^\circ} = 50{^\circ}.\]
\[Ответ:\ \ \angle AOC = 50{^\circ};\ \angle ABC = 25{^\circ}.\]