| ( | 160 | − | x | ) | ( | 200 | + | 4 | x | ) | = | 41600 |
| Left side of the equation = | 160 | ( | 200 | + | 4 | x | ) | − | x | ( | 200 | + | 4 | x | ) |
| = | 160 | × | 200 | + | 160 | × | 4 | x | − | x | ( | 200 | + | 4 | x | ) |
| = | 32000 | + | 640 | x | − | x | ( | 200 | + | 4 | x | ) |
| = | 32000 | + | 640 | x | − | x | × | 200 | − | x | × | 4 | x |
| = | 32000 | + | 440 | x | − | x | × | 4 | x |
| 32000 | + | 440 | x | − | x | × | 4 | x | = | 41600 |