$\frac{4x - 1}{12} + \frac{7}{4} = \frac{5 - x}{9}$
$\frac{4x - 1 + 3 * 7}{12} = \frac{5 - x}{9}$
$\frac{4x + 20}{12} = \frac{5 - x}{9}$
$\frac{4(x + 5)}{12} = \frac{5 - x}{9}$
$\frac{x + 5}{3} = \frac{5 - x}{9}$ | * 9
3(x + 5) = 5 − x
3x + 15 = 5 − x
3x + x = 5 − 15
4x = −10
x = −2,5

$\frac{2x - 9}{6} - \frac{2(5x + 3)}{15} = \frac{1}{2}$
$\frac{2x - 9}{6} - \frac{1}{2} = \frac{2(5x + 3)}{15}$
$\frac{2x - 9 - 3}{6} = \frac{2(5x + 3)}{15}$
$\frac{2x - 12}{6} = \frac{2(5x + 3)}{15}$
$\frac{2(x - 6)}{6} = \frac{2(5x + 3)}{15}$
$\frac{x - 6}{3} = \frac{2(5x + 3)}{15}$ | * 15
5(x − 6) = 2(5x + 3)
5x − 30 = 10x + 6
5x − 10x = 6 + 30
−5x = 36
x = −7,2