| 30 | ( | x | + | 1 | ) | × | 9 10 | = | 30 | x | − | 18 |
| Left side of the equation = | 27 | ( | x | + | 1 | ) |
| 27 | ( | x | + | 1 | ) | = | 30 | x | − | 18 |
| Left side of the equation = | 27 | x | + | 27 | × | 1 |
| = | 27 | x | + | 27 |
| 27 | x | + | 27 | = | 30 | x | − | 18 |
| 27 | x | − | 30 | x | = | - | 18 | − | 27 |
| - | 3 | x | = | - | 18 | − | 27 |
| - | 3 | x | = | - | 45 |
| 45 | = | 3 | x |
| 3 | x | = | 45 |
| x | = | 45 | ÷ | 3 |
| = | 45 | × | 1 3 |
| = | 15 | × | 1 |
| x | = | 15 |