| X | × | 20 | × | 4 5 | = | 20 | X | − | 140 | × | 9 10 |
| Left side of the equation = | X | × | 16 |
| 16 | X | = | 20 | X | − | 140 | × | 9 10 |
| Right side of the equation = | 20 | X | − | 126 |
| 16 | X | = | 20 | X | − | 126 |
| 16 | X | − | 20 | X | = | - | 126 |
| - | 4 | X | = | - | 126 |
| 126 | = | 4 | X |
| 4 | X | = | 126 |
| X | = | 126 | ÷ | 4 |
| = | 126 | × | 1 4 |
| = | 63 | × | 1 2 |
| X | = | 63 2 |
| X | = | 31.5 |