\[Вершины\ треугольника\ ABC:\]
\[A(3;\ - 2),\ \ \ B(2;\ 3),\ \ \ C(7;\ 4).\]
\[1)\ Середина\ AC:\]
\[x = \frac{3 + 7}{2} = 5;\ \ \ \]
\[y = \frac{- 2 + 4}{2} = 1.\]
\[2)\ BM = \sqrt{(2 - 5)^{2} + (3 - 1)^{2}} =\]
\[= \sqrt{3^{2} + 2^{2}} = \sqrt{9 + 4} = \sqrt{13}.\]
\[Ответ:\ \ \sqrt{13}.\]