\[\boxed{\mathbf{35}.}\]
\[1)\ (5 - 2a)x = a\]
\[x = \frac{a}{5 - 2a}\]
\[5 - 2a \neq 0\]
\[- 2a \neq - 5\]
\[a \neq 2,5.\]
\[Ответ:при\ a = \neq 2,5.\]
\[2)\ ax + 3 - 2x = 3\]
\[ax - 2x = 0\]
\[x(a - 2) = 0\]
\[a - 2 \neq 0\]
\[a \neq 2.\]
\[Ответ:при\ a \neq 2.\]