Номер 10 1,2,3
номер11. 1, 2, 3
номер 12. 1, 2​

10.

1) 2x = 18 - x

2x + x = 18

3x = 18

x = 18 / 3

x = 6

2) 7x + 3 = 30 - 2x

7x + 2x = 30 - 3

9x = 27

x = 27 / 9

x = 3

3) 7 - 2x = 3x - 18

-2x - 3x = -18 - 7

-5x = -25

5x = 25

x = 25 / 5

x = 5

11.

1) 3(x - 2) = x + 2

3x - 6 = x + 2

3x - x = 2 + 6

2x = 8

x = 8 / 2

x = 4

2) 5 - 2(x - 1) = 4 - x

5 - 2x + 2 = 4 - x

-2x + x = 4 - 5 - 2

-x = -11

x = 11

3) (7x - 1) - (9x + 3) = 5

7x - 1 - 9x - 3 = 5

7x - 9x = 5 + 1 + 3

-2x = 9

-x = 9 / 2

-x = 4.5

x = -4.5

12.

1) 3x + 6 = 2(2x - 7) - x

3x + 6 = 4x - 14 - x

3x - 4x + x = - 14 - 6

0x ≠ -20

x = -20/0

x = ∅

2) 6,2(3 - 2x) = 20 - (12,4x + 1,4)

18,6 - 12,4x = 20 - 12,4x - 1,4

-12,4x + 12,4x = 20 - 1,4 - 18,6

0 = 0

x = R