| ( | 1 | − | x | ) | ( | 200 | − | 400 | x | ) | = | 224 |
| Left side of the equation = | 1 | ( | 200 | − | 400 | x | ) | − | x | ( | 200 | − | 400 | x | ) |
| = | 1 | × | 200 | − | 1 | × | 400 | x | − | x | ( | 200 | − | 400 | x | ) |
| = | 200 | − | 400 | x | − | x | ( | 200 | − | 400 | x | ) |
| = | 200 | − | 400 | x | − | x | × | 200 | + | x | × | 400 | x |
| = | 200 | − | 600 | x | + | x | × | 400 | x |
| 200 | − | 600 | x | + | x | × | 400 | x | = | 224 |