| ( | X | − | ( | ( | X | − | X | × | 1 5 | ) | × | 1 5 | ) | ) | = | 4000 |
| Left side of the equation = | X | − | ( | ( | X | − | X | × | 1 5 | ) | × | 1 5 | ) |
| = | X | − | ( | X | − | X | × | 1 5 | ) | × | 1 5 |
| = | X | − | X | × | 1 5 | + | X | × | 1 5 | × | 1 5 |
| = | X | − | X | × | 1 5 | + | X | × | 1 25 |
| = | 21 25 | X |
21 25 | X | = | 4000 |
| X | = | 4000 | ÷ | 21 25 |
| = | 4000 | × | 25 21 |
| X | = | 100000 21 |
| X | = | 4761.904762 |