$x - \frac{7x + 1}{8} = \frac{4x + 3}{4}$
$x - \frac{7x + 1}{8} - \frac{4x + 3}{4} = 0$
$\frac{8x - 7x - 1 - 2(4x + 3)}{8} = 0$
$\frac{8x - 7x - 1 - 8x - 6}{8} = 0$
8x − 7x − 1 − 8x − 6 = 0
−7x = 6 + 1
x = 7 : (−7)
x = −1

$\frac{2x + 1}{6} - \frac{3x + 1}{7} = 2$
$\frac{7(2x + 1) - 6(3x + 1)}{42} = 2$
7(2x + 1) − 6(3x + 1) = 2 * 42
14x + 7 − 18x − 6 = 84
−4x = 84 − 7 + 6
−4x = 83
$x = -\frac{83}{4}$
$x = -20\frac{3}{4}$
x = −20,75

$\frac{2x + 3}{3} - \frac{5x + 13}{6} + \frac{5 - 2x}{2} = 6$
$\frac{2(2x + 3) - (5x + 13) + 3(5 - 2x)}{6} = 6$
2(2x + 3) − (5x + 13) + 3(5 − 2x) = 6 * 6
4x + 6 − 5x − 13 + 15 − 6x = 36
4x − 5x − 6x = 36 − 6 + 13 − 15
−7x = 28
x = 28 : −7
x = −4

$\frac{4x^2 + 5x}{14} + \frac{10 - 2x^2}{7} = 5$
$\frac{4x^2 + 5x + 2(10 - 2x^2)}{14} = 5$
$4x^2 + 5x + 2(10 - 2x^2) = 5 * 14$
$4x^2 + 5x + 20 - 4x^2 = 70$
5x = 70 − 20
x = 50 : 5
x = 10