\[\boxed{\mathbf{118.}}\]
\[Девочек\ в\ группе:\]
\[18 - 7 = 11.\]
\[\frac{11}{18} \cdot \frac{10}{17} + \frac{7}{18} \cdot \frac{6}{17} =\]
\[= \frac{55}{9 \cdot 17} + \frac{21}{9 \cdot 17} = \frac{76}{153}.\]
\[Ответ:\ \frac{76}{153}.\]