40 100 | = | ( | 129 | − | X | ) | ÷ | 129 | × | 100 100 |
| Right side of the equation = | ( | 129 | − | X | ) | × | 1 129 |
40 100 | = | ( | 129 | − | X | ) | × | 1 129 |
| Right side of the equation = | 129 | × | 1 129 | − | X | × | 1 129 |
| = | 1 | − | X | × | 1 129 |
40 100 | = | 1 | − | 1 129 | X |
1 129 | X | = | 1 | − | 40 100 |
1 129 | X | = | 3 5 |
| X | = | 3 5 | ÷ | 1 129 |
| = | 3 5 | × | 129 |
| X | = | 387 5 |
| X | = | 77.4 |