| 10 | + | 10 | ( | x | + | 1 | ) | + | 10 | ( | x | + | 1 | ) | = | 0 |
| Left side of the equation = | 10 | + | 10 | x | + | 10 | × | 1 | + | 10 | ( | x | + | 1 | ) |
| = | 10 | + | 10 | x | + | 10 | + | 10 | ( | x | + | 1 | ) |
| = | 20 | + | 10 | x | + | 10 | ( | x | + | 1 | ) |
| = | 20 | + | 10 | x | + | 10 | x | + | 10 | × | 1 |
| = | 20 | + | 10 | x | + | 10 | x | + | 10 |
| = | 30 | + | 20 | x |
| 30 | + | 20 | x | = | 0 |
| 20 | x | = | 0 | − | 30 |
| 20 | x | = | - | 30 |
| x | = | - | 30 | ÷ | 20 |
| = | - | 30 | × | 1 20 |
| = | - | 3 | × | 1 2 |
| x | = | - | 3 2 |
| x | = | - 1.5 |