2х +(5-7х) = 15
2х + 5 - 7х = 15
-5х + 5 = 15
-5х = 15 - 5
-5х=10
х= 10 : (-5)
х = - 2
===================
2 *(-2) + (5 - 7 *(-2) ) = 15
- 4 + (5 +14) = 15
- 4 + 19 = 15
15 = 15
5х + 3 =-3х + 19
5х +3х = 19 - 3
8х = 16
х= 16:8
х= 2
================
5*2 +3 = -3 * 2 +19
10 + 3 = -6 + 19
13 = 13
3х + 4(5-3х) = -7
3х + 4*5 + 4*(-3х) = -7
3х + 20 - 12х = -7
-9х + 20 = -7
-9х = -7 - 20
-9х = -27
х= -27 :(-9)
х= 3
================
3*3 +4*(5 - 3*3) = -7
9 + 4* (5 - 9) = - 7
9 + 4 * (-4) = -7
9 - 16 = -7
-7 = -7
¹/₃ х +1 = ¹/₂ (х - ¹/₆)
¹/₃ х + 1 = ¹/₂ х - ¹/₂ * ¹/₆
¹/₃ х + 1 = ¹/₂ х - ¹/₁₂
¹/₃ х - ¹/₂ х = - ¹/₁₂ - 1
(¹/₃ - ¹/₂) * х = - 1 ¹/₁₂
(²/₆ - ³/₆) х = - 1 ¹/₁₂
- ¹/₆ х = - ¹³/₁₂
х= - ¹³/₁₂ : (-¹/₆) = - ¹³/₁₂ * (-⁶/₁) = ¹³/₂
х = 6 ¹/₂
==========================
¹/₃ * 6 ¹/₂ + 1 = ¹/₂ *(6 ¹/₂ - ¹/₆)
¹/₃ * ¹³/₂ + 1 = ¹/₂ * (6 ³/₆ - ¹/₆)
¹³/₆ + 1 = ¹/₂ * 6 ¹/₃
2 ¹/₆ + 1 = ¹/₂ * ¹⁹/₃
3 ¹/₆ = ¹⁹/₆
3 ¹/₆ = 3 ¹/₆