3 х=28-х 5 х+12=8 х+30 33+8 х=-5 х+72

3 х = 28 - х; 5 х + 12 = 8 х + 30; 33 + 8 х = - 5 х + 72;

Решим уравнения:

1. 3x = 28 - x

3x - x = 28

2x = 28

x = 14;

2. 5x + 12 = 8x + 30

5x - 8x = 30 - 12

-3x = 18

x = - 6;

3. 33 + 8x = - 5x + 72

8x - 5x = 72 - 33

13x = 39

x = 3;

Ответ: 1. x = 14; 2. x = - 6; 3. x = 3;