| ( | ( | X | − | 300 | ) | − | ( | 4000 | × | 12 100 | ) | ) | ÷ | 800 | = | ( | ( | X | − | 300 | ) | ) | ÷ | 1000 |
| Left side of the equation = | ( | X | − | 300 | ) | × | 1 800 | − | ( | 4000 | × | 12 100 | ) | × | 1 800 |
| = | X | × | 1 800 | − | 300 | × | 1 800 | − | ( | 4000 | × | 12 100 | ) | × | 1 800 |
| = | X | × | 1 800 | − | 3 8 | − | ( | 4000 | × | 12 100 | ) | × | 1 800 |
| = | 1 800 | X | − | 3 8 | − | 4000 | × | 12 100 | × | 1 800 |
| = | 1 800 | X | − | 3 8 | − | 3 5 |
| = | 1 800 | X | − | 39 40 |
1 800 | X | − | 39 40 | = | ( | ( | X | − | 300 | ) | ) | ÷ | 1000 |
| Right side of the equation = | ( | X | − | 300 | ) | × | 1 1000 |
| = | X | × | 1 1000 | − | 300 | × | 1 1000 |
| = | X | × | 1 1000 | − | 3 10 |
1 800 | X | − | 39 40 | = | 1 1000 | X | − | 3 10 |
1 800 | X | − | 1 1000 | X | = | - | 3 10 | + | 39 40 |
1 4000 | X | = | - | 3 10 | + | 39 40 |
1 4000 | X | = | 27 40 |
| X | = | 27 40 | ÷ | 1 4000 |
| = | 27 40 | × | 4000 |
| = | 27 | × | 100 |
| X | = | 2700 |