| ( | 2 | x | + | 20 | ) | ( | x | − | 259 | ) | = | 1200 |
| Left side of the equation = | 2 | x | ( | x | − | 259 | ) | + | 20 | ( | x | − | 259 | ) |
| = | 2 | x | x | − | 2 | x | × | 259 | + | 20 | ( | x | − | 259 | ) |
| = | 2 | x | x | − | 518 | x | + | 20 | ( | x | − | 259 | ) |
| = | 2 | x | x | − | 518 | x | + | 20 | x | − | 20 | × | 259 |
| = | 2 | x | x | − | 518 | x | + | 20 | x | − | 5180 |
| = | 2 | x | x | − | 498 | x | − | 5180 |
| 2 | x | x | − | 498 | x | − | 5180 | = | 1200 |