| 180 | × | 900 | = | ( | 1800 | + | x | ) | ( | 180 | − | x | ) |
| Left side of the equation = | 162000 |
| 162000 | = | ( | 1800 | + | x | ) | ( | 180 | − | x | ) |
| Right side of the equation = | 1800 | ( | 180 | − | x | ) | + | x | ( | 180 | − | x | ) |
| = | 1800 | × | 180 | − | 1800 | x | + | x | ( | 180 | − | x | ) |
| = | 324000 | − | 1800 | x | + | x | ( | 180 | − | x | ) |
| = | 324000 | − | 1800 | x | + | x | × | 180 | − | x | x |
| = | 324000 | − | 1620 | x | − | x | x |
| 162000 | = | 324000 | − | 1620 | x | − | x | x |