| ( | X | − | 165 | ) | × | 12 | − | ( | 1500 | + | 250 | × | 12 | ) | = | 0 |
| Left side of the equation = | X | × | 12 | − | 165 | × | 12 | − | ( | 1500 | + | 250 | × | 12 | ) |
| = | X | × | 12 | − | 1980 | − | ( | 1500 | + | 250 | × | 12 | ) |
| = | 12 | X | − | 1980 | − | 1500 | − | 250 | × | 12 |
| = | 12 | X | − | 1980 | − | 1500 | − | 3000 |
| = | 12 | X | − | 6480 |
| 12 | X | − | 6480 | = | 0 |
| 12 | X | = | 0 | + | 6480 |
| 12 | X | = | 6480 |
| X | = | 6480 | ÷ | 12 |
| = | 6480 | × | 1 12 |
| = | 540 | × | 1 |
| X | = | 540 |