| ( | 160 | − | x | ) | ( | 20000 | + | 1000 | x | ) | = | 0 |
| Left side of the equation = | 160 | ( | 20000 | + | 1000 | x | ) | − | x | ( | 20000 | + | 1000 | x | ) |
| = | 160 | × | 20000 | + | 160 | × | 1000 | x | − | x | ( | 20000 | + | 1000 | x | ) |
| = | 3200000 | + | 160000 | x | − | x | ( | 20000 | + | 1000 | x | ) |
| = | 3200000 | + | 160000 | x | − | x | × | 20000 | − | x | × | 1000 | x |
| = | 3200000 | + | 140000 | x | − | x | × | 1000 | x |
| 3200000 | + | 140000 | x | − | x | × | 1000 | x | = | 0 |