\[\boxed{\mathbf{1138.}}\]
\[C - выпадение\ дубля;\ \]
\[\overline{C} - искомое:\]
\[n = 28;\ \]
\[P(C) = \frac{7}{28} = \frac{1}{4};\]
\[P\left( \overline{C} \right) = 1 - P(C) = 1 - \frac{1}{4} = \frac{3}{4}.\]
\[Ответ:\ \ \frac{3}{4}.\]