а) 2x = -5
\[ x = \frac{-5}{2} \]
б) 5x - 6 = x + 2
\[ 5x - x = 2 + 6 \]
\[ 4x = 8 \]
\[ x = \frac{8}{4} \]
\[ x = 2 \]
Ответ: а) \( x = -2.5 \); б) \( x = 2 \).