| N | × | 129 | × | 1 5 | + | 400 | = | N | × | 129 | × | 1 2 | − | 400 |
| Left side of the equation = | N | × | 129 5 | + | 400 |
129 5 | N | + | 400 | = | N | × | 129 | × | 1 2 | − | 400 |
| Right side of the equation = | N | × | 129 2 | − | 400 |
129 5 | N | + | 400 | = | 129 2 | N | − | 400 |
129 5 | N | − | 129 2 | N | = | - | 400 | − | 400 |
| - | 387 10 | N | = | - | 400 | − | 400 |
| - | 387 10 | N | = | - | 800 |
| 800 | = | 387 10 | N |
387 10 | N | = | 800 |
| N | = | 800 | ÷ | 387 10 |
| = | 800 | × | 10 387 |
| N | = | 8000 387 |
| N | = | 20.671835 |