| ( | 1 | − | x | ) | ( | 600 | + | x | ÷ | 1 10 | × | 120 | ) | + | 600 | = | 1200 |
| Left side of the equation = | 1 | ( | 600 | + | x | ÷ | 1 10 | × | 120 | ) | − | x | ( | 600 | + | x | ÷ | 1 10 | × | 120 | ) | + | 600 |
| = | 1 | × | 600 | + | 1 | x | ÷ | 1 10 | × | 120 | − | x | ( | 600 | + | x | ÷ | 1 10 | × | 120 | ) | + | 600 |
| = | 600 | + | 1200 | x | − | x | ( | 600 | + | x | ÷ | 1 10 | × | 120 | ) | + | 600 |
| = | 1200 | + | 1200 | x | − | x | ( | 600 | + | x | ÷ | 1 10 | × | 120 | ) |
| = | 1200 | + | 1200 | x | − | x | × | 600 | − | x | x | ÷ | 1 10 | × | 120 |
| = | 1200 | + | 1200 | x | − | x | × | 600 | − | x | x | × | 1200 |
| = | 1200 | + | 600 | x | − | x | x | × | 1200 |
| 1200 | + | 600 | x | − | x | x | × | 1200 | = | 1200 |
| x2= | 1 2 |