| ( | 4000 | + | 100 | x | − | 500 | ) | ( | 100 | − | x | ) | − | 100 | x | = | 404000 |
| Left side of the equation = | 4000 | ( | 100 | − | x | ) | + | 100 | x | ( | 100 | − | x | ) | − | 500 | ( | 100 | − | x | ) | − | 100 | x |
| = | 4000 | × | 100 | − | 4000 | x | + | 100 | x | ( | 100 | − | x | ) | − | 500 | ( | 100 | − | x | ) | − | 100 | x |
| = | 400000 | − | 4000 | x | + | 100 | x | ( | 100 | − | x | ) | − | 500 | ( | 100 | − | x | ) | − | 100 | x |
| = | 400000 | − | 4100 | x | + | 100 | x | ( | 100 | − | x | ) | − | 500 | ( | 100 | − | x | ) |
| = | 400000 | − | 4100 | x | + | 100 | x | × | 100 | − | 100 | x | x | − | 500 | ( | 100 | − | x | ) |
| = | 400000 | − | 4100 | x | + | 10000 | x | − | 100 | x | x | − | 500 | ( | 100 | − | x | ) |
| = | 400000 | + | 5900 | x | − | 100 | x | x | − | 500 | ( | 100 | − | x | ) |
| = | 400000 | + | 5900 | x | − | 100 | x | x | − | 500 | × | 100 | + | 500 | x |
| = | 400000 | + | 5900 | x | − | 100 | x | x | − | 50000 | + | 500 | x |
| = | 350000 | + | 6400 | x | − | 100 | x | x |
| 350000 | + | 6400 | x | − | 100 | x | x | = | 404000 |