| 9 | ( | 3 | x | + | 12 | ) | + | 9 | ( | 6 | x | + | 15 | ) | + | 5 | = | 5 |
| Left side of the equation = | 9 | × | 3 | x | + | 9 | × | 12 | + | 9 | ( | 6 | x | + | 15 | ) | + | 5 |
| = | 27 | x | + | 108 | + | 9 | ( | 6 | x | + | 15 | ) | + | 5 |
| = | 27 | x | + | 113 | + | 9 | ( | 6 | x | + | 15 | ) |
| = | 27 | x | + | 113 | + | 9 | × | 6 | x | + | 9 | × | 15 |
| = | 27 | x | + | 113 | + | 54 | x | + | 135 |
| = | 81 | x | + | 248 |
| 81 | x | + | 248 | = | 5 |
| 81 | x | = | 5 | − | 248 |
| 81 | x | = | - | 243 |
| x | = | - | 243 | ÷ | 81 |
| = | - | 243 | × | 1 81 |
| = | - | 3 | × | 1 |
| x | = | - | 3 |