2. 20х = -2; 3. 2х + 4 = 0;
4. 7х – 2 = 4;
5. 12 – 2х = 3х;
6. 5х – 8 = 9 + 3х;
7. 9х + (6 – 2х) = 15;
8. 2х – (5х + 4) = - 8;
9. 5 – 3(2х – 7) = -6х;
10. 4(5х +8) – 2х = 12;
11. (х – 5)(х+9) = 0;
12. (3х – 4)(2х + 7) = 0.