12.
a)
[tex] \frac{x}{3} + 1 = \frac{5}{6} + \frac{x}{2} | \times 6 \\ 2x + 6 = 5 + 3x \\ - x = - 1 \\ x = 1[/tex]
b)
[tex] \frac{2x - 3}{4} = \frac{1}{2} + x | \times 4 \\ 2x - 3 = 2 + 4x \\ - 2x = 5 \\ x = - 2.5[/tex]
13.
a)
[tex](x + 3)(x + 2) - {x}^{2} = 0 \\ {x}^{2} + 2x + 3x + 6 - {x}^{2} = 0 \\ 5x = - 6 \\ x = - \frac{6}{5} [/tex]
b)
[tex](x - 4)(x + 5) - {x}^{2} = 3 \\ {x}^{2} + 5x - 4x - 20 - {x}^{2} = 3 \\ x = 23[/tex]
