$5(\frac{x}{3} + \frac{x}{6} + 7) + 12 = 7(\frac{x}{3} + \frac{x}{6} + 7) - 4$
пусть $\frac{x}{3} + \frac{x}{6} + 7 = y$, тогда:
5y + 12 = 7y − 4
5y − 7y = −4 − 12
−2y = −16
y = 8
$\frac{x}{3} + \frac{x}{6} + 7 = 8$
$\frac{x}{3} + \frac{x}{6} = 8 - 7$ |*6
2x + x = 6(8 − 7)
3x = 6
x = 2

$1 - 2(\frac{x}{5} - \frac{x}{3} - 5) = 14 + (\frac{x}{5} - \frac{x}{3} - 6)$
пусть $\frac{x}{5} - \frac{x}{3} = y$, тогда:
1 − 2(y − 5) = 14 + (y − 6)
1 − 2y + 10 = 14 + y − 6
−2y − y = 8 − 11
−3y = −3
y = 1
$\frac{x}{5} - \frac{x}{3} = 1$
3x − 5x = 15
−2x = 15
x = −7,5

7(2(5x + 1) − 3) − 15 = 4(2(5x + 1) − 3)
пусть 2(5x + 1) − 3 = y
7y − 15 = 4y
7y − 4y = 15
3y = 15
y = 5
2(5x + 1) − 3 = 5
10x + 2 = 5 + 3
10x = 8 − 2
10x = 6
x = 0,6

4(3(2x − 1) + 7) − 4 = 3(3(2x − 1) + 6)
пусть 3(2x − 1) = y
4(y + 7) − 4 = 3(y + 6)
4y + 28 − 4 = 3y + 18
4y − 3y = 18 − 24
y = −6
3(2x − 1) = −6
6x − 3 = −6
6x = −3
x = −0,5