| ( | 2 | x | + | 20 | ) | ( | 299 | − | x | ) | = | 1200 |
| Left side of the equation = | 2 | x | ( | 299 | − | x | ) | + | 20 | ( | 299 | − | x | ) |
| = | 2 | x | × | 299 | − | 2 | x | x | + | 20 | ( | 299 | − | x | ) |
| = | 598 | x | − | 2 | x | x | + | 20 | ( | 299 | − | x | ) |
| = | 598 | x | − | 2 | x | x | + | 20 | × | 299 | − | 20 | x |
| = | 598 | x | − | 2 | x | x | + | 5980 | − | 20 | x |
| = | 578 | x | − | 2 | x | x | + | 5980 |
| 578 | x | − | 2 | x | x | + | 5980 | = | 1200 |