| 1800 | ( | x | + | 1 | ) | × | 70 100 | = | 0 |
| Left side of the equation = | 1260 | ( | x | + | 1 | ) |
| 1260 | ( | x | + | 1 | ) | = | 0 |
| Left side of the equation = | 1260 | x | + | 1260 | × | 1 |
| = | 1260 | x | + | 1260 |
| 1260 | x | + | 1260 | = | 0 |
| 1260 | x | = | 0 | − | 1260 |
| 1260 | x | = | - | 1260 |
| x | = | - | 1260 | ÷ | 1260 |
| = | - | 1260 | × | 1 1260 |
| = | - | 1 | × | 1 |
| x | = | - | 1 |