Рассмотрим два случая:
\[ 2 - 7x = 9 \]
\[ -7x = 9 - 2 \]
\[ -7x = 7 \]
\[ x = \frac{7}{-7} \]
\[ x = -1 \]
\[ 2 - 7x = -9 \]
\[ -7x = -9 - 2 \]
\[ -7x = -11 \]
\[ x = \frac{-11}{-7} \]
\[ x = \frac{11}{7} \]
Ответ: x = -1, x = \frac{11}{7}