I. --- 3
[tex]x - (1 + 2x) = 5 \\ x - 1 - 2x = 5 \\ - x = 6 \\ x = - 6[/tex]
II. --- 1
[tex] \frac{1}{3} (5x + 2) = 1 - x \\ 5x + 2 = 3 - 3x \\ 8x = 1 \\ x = \frac{1}{8} [/tex]
III. --- 2
[tex]2x + 8 = - (6x - 7) \\ 2x + 8 = - 6x + 7 \\ 8x = - 1 \\ x = - \frac{1}{8} [/tex]