| 3 | ( | X | − | 1 | ) | − | 4 | ( | X | + | 3 | ) | = | 4 | X |
| Left side of the equation = | 3 | X | − | 3 | × | 1 | − | 4 | ( | X | + | 3 | ) |
| = | 3 | X | − | 3 | − | 4 | ( | X | + | 3 | ) |
| = | 3 | X | − | 3 | − | 4 | X | − | 4 | × | 3 |
| = | 3 | X | − | 3 | − | 4 | X | − | 12 |
| = | - | 1 | X | − | 15 |
| - | 1 | X | − | 15 | = | 4 | X |
| - | 1 | X | − | 4 | X | = | 15 |
| - | 5 | X | = | 15 |
| - | 15 | = | 5 | X |
| 5 | X | = | - | 15 |
| X | = | - | 15 | ÷ | 5 |
| = | - | 15 | × | 1 5 |
| = | - | 3 | × | 1 |
| X | = | - | 3 |