| 81 | ( | x | − | 2 | ) | = | 69 | ( | x | + | 2 | ) |
| Left side of the equation = | 81 | x | − | 81 | × | 2 |
| = | 81 | x | − | 162 |
| 81 | x | − | 162 | = | 69 | ( | x | + | 2 | ) |
| Right side of the equation = | 69 | x | + | 69 | × | 2 |
| = | 69 | x | + | 138 |
| 81 | x | − | 162 | = | 69 | x | + | 138 |
| 81 | x | − | 69 | x | = | 138 | + | 162 |
| 12 | x | = | 138 | + | 162 |
| 12 | x | = | 300 |
| x | = | 300 | ÷ | 12 |
| = | 300 | × | 1 12 |
| = | 25 | × | 1 |
| x | = | 25 |