| ( | 60 | − | x | ) | ( | 200 | + | 10 | x | ) | − | ( | 1200 | − | 20 | x | ) | = | 14000 |
| Left side of the equation = | 60 | ( | 200 | + | 10 | x | ) | − | x | ( | 200 | + | 10 | x | ) | − | ( | 1200 | − | 20 | x | ) |
| = | 60 | × | 200 | + | 60 | × | 10 | x | − | x | ( | 200 | + | 10 | x | ) | − | ( | 1200 | − | 20 | x | ) |
| = | 12000 | + | 600 | x | − | x | ( | 200 | + | 10 | x | ) | − | ( | 1200 | − | 20 | x | ) |
| = | 12000 | + | 600 | x | − | x | × | 200 | − | x | × | 10 | x | − | ( | 1200 | − | 20 | x | ) |
| = | 12000 | + | 400 | x | − | x | × | 10 | x | − | ( | 1200 | − | 20 | x | ) |
| = | 12000 | + | 400 | x | − | x | × | 10 | x | − | 1200 | + | 20 | x |
| = | 10800 | + | 420 | x | − | x | × | 10 | x |
| 10800 | + | 420 | x | − | x | × | 10 | x | = | 14000 |