1) 7x - (3 + 2x) = x + 9;
2) 13 - (2x - 5) = x - 3;
3) 3x – (10 - 9x) = 223;
4) 26 - (17 – 2x) = 5x.​

Пошаговое объяснение:

1) 7x - (3 + 2x) = x + 9;

7x - 3 - 2x = x + 9

5x - 3 = x + 9

5x - x = 9 + 3

4x = 12

x = 12 : 4

x = 3

2) 13 - (2x - 5) = x - 3;

13 - 2x + 5 = x - 3

18 - 2x = x - 3

x + 2x = 18 + 3

3x = 21

x = 21 : 3

x = 7

3) 3x – (10 - 9x) = 223;

3x - 10 + 9x = 223

12x - 10 = 223

12x = 223 + 10

12x = 233

x = 233 : 12

x = 19 5/12

4) 26 - (17 – 2x) = 5x.​

26 - 17 + 2x = 5x

9 + 2x = 5x

5x - 2x = 9

3x = 9

x = 9 : 3

x = 3