| 4 | x | − | 3 | ( | 20 | − | x | ) | × | 3 | = | 6 | x | − | 7 | ( | 9 | − | x | ) |
| Left side of the equation = | 4 | x | − | 9 | ( | 20 | − | x | ) |
| 4 | x | − | 9 | ( | 20 | − | x | ) | = | 6 | x | − | 7 | ( | 9 | − | x | ) |
| Left side of the equation = | 4 | x | − | 9 | × | 20 | + | 9 | x |
| = | 4 | x | − | 180 | + | 9 | x |
| = | 13 | x | − | 180 |
| 13 | x | − | 180 | = | 6 | x | − | 7 | ( | 9 | − | x | ) |
| Right side of the equation = | 6 | x | − | 7 | × | 9 | + | 7 | x |
| = | 6 | x | − | 63 | + | 7 | x |
| = | 13 | x | − | 63 |
| 13 | x | − | 180 | = | 13 | x | − | 63 |
| 13 | x | − | 13 | x | = | - | 63 | + | 180 |
| 0 | x | = | - | 63 | + | 180 |
| 0 | x | = | 117 |