\[Схематический\ рисунок.\]
\[Дано:\]
\[MK \parallel BC;\]
\[AM = 9\ см;\]
\[BM = 6\ см;\]
\[KC = 8\ см.\]
\[Найти:\]
\[\text{AK.}\]
\[Решение.\]
\[По\ теореме\ Фалеса:\]
\[\frac{\text{AM}}{\text{AK}} = \frac{\text{BM}}{\text{KC}}\]
\[AK = \frac{AM \bullet KC}{\text{BM}}\]
\[AK = \frac{9 \bullet 8}{6} = 3 \bullet 4 = 12\ см.\]
\[Ответ:\ \ 12\ см.\]