| 1287 | − | ( | 1287 | × | 40 | ÷ | 300 | ) | − | 100 | − | 120 | = | x |
| Left side of the equation = | 1067 | − | ( | 1287 | × | 40 | ÷ | 300 | ) |
| 1067 | − | ( | 1287 | × | 40 | ÷ | 300 | ) | = | x |
| Left side of the equation = | 1067 | − | 1287 | × | 40 | ÷ | 300 |
| = | 1067 | − | 858 5 |
| = | 4477 5 |
4477 5 | = | x |
| - | x | = | - | 4477 5 |
4477 5 | = | x |
| x | = | 4477 5 |