Giải các phương trình sau:

a) $8 + 2\left( {x - 1} \right) = 20$

b) $4\left( {3x - 2} \right) + 3\left( {x - 4} \right) = 7x + 20$

c) $\frac{{2x}}{3} + x = \frac{{2x + 5}}{6} + \frac{1}{2}$

a) $8 + 2\left( {x - 1} \right) = 20$

$\begin{array}{l}8 + 2x - 2 = 20\\2x + 6 = 20\\2x = 20 - 6\\2x = 14\\x = 7\end{array}$

Vậy $x = 7$

b) $4\left( {3x - 2} \right) + 3\left( {x - 4} \right) = 7x + 20$

$\begin{array}{l}12x - 8 + 3x - 12 = 7x + 20\\12x + 3x - 7x = 20 + 8 + 12\\8x = 40\\x = 5\end{array}$

Vậy $x = 5$

c) $\frac{{2x}}{3} + x = \frac{{2x + 5}}{6} + \frac{1}{2}$

$\begin{array}{l}\frac{{2.2x}}{6} + \frac{{6x}}{6} = \frac{{2x + 5}}{6} + \frac{3}{6}\\4x + 6x = 2x + 5 + 3\\10x - 2x = 8\\8x = 8\\x = 1\end{array}$

Vậy $x = 1$