а) 2x = -3
\[ x = \frac{-3}{2} \]
б) 4x - 7 = x + 2
\[ 4x - x = 2 + 7 \]
\[ 3x = 9 \]
\[ x = \frac{9}{3} \]
\[ x = 3 \]
Ответ: а) \( x = -1.5 \); б) \( x = 3 \).