| ( | X | + | 50 100 | X | ) | × | 90 100 | − | 50 | − | X | = | 1000 |
| Left side of the equation = | X | × | 90 100 | + | 50 100 | X | × | 90 100 | − | 50 | − | X |
| = | X | × | 90 100 | + | 9 20 | X | − | 50 | − | X |
| = | 7 20 | X | − | 50 |
7 20 | X | − | 50 | = | 1000 |
7 20 | X | = | 1000 | + | 50 |
7 20 | X | = | 1050 |
| X | = | 1050 | ÷ | 7 20 |
| = | 1050 | × | 20 7 |
| = | 150 | × | 20 |
| X | = | 3000 |