1. - 12x + 11x=20 -40
- x= - 20
x=20
2. 6x - 5x = 15 - 10
x = 5
3. - 5n + 4n = 10 - 8
- n = 2
n = -2
4. 10a - 9a = 5 - 7
a = - 2
5. - 15y + 14y = 40 - 30
y = - 10
6. 6x - 7x = 3 - 5
x = 2
7. 3x - 4x = 1 - 6
x = 5
8. 4x - 8 = -3x + 6
4x + 3x = 6 + 8
7x = 14
x = 2
9. 0.6y - 0.4y = 4
y = 20
10. -0.5x= - 0.5
x = 1
11. - 0.4y = - 0.4
y = 1
12. 3x - 8 = 5x - 3
- 2x = 5
x = -2.5