| ( | ( | X | × | 12 | − | ( | 5000 | + | 1500 | + | 2000 | ) | × | 12 | ) | × | 10 100 | − | 2520 | ) | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 10 100 | − | 1410 | ) | × | 12 | = | 4000 |
| Left side of the equation = | ( | X | × | 12 | − | ( | 5000 | + | 1500 | + | 2000 | ) | × | 12 | ) | × | 10 100 | − | 2520 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 10 100 | − | 1410 | ) | × | 12 |
| = | X | × | 12 | × | 10 100 | − | ( | 5000 | + | 1500 | + | 2000 | ) | × | 12 | × | 10 100 | − | 2520 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 10 100 | − | 1410 | ) | × | 12 |
| = | X | × | 6 5 | − | ( | 5000 | + | 1500 | + | 2000 | ) | × | 6 5 | − | 2520 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 10 100 | − | 1410 | ) | × | 12 |
| = | 6 5 | X | − | 5000 | × | 6 5 | − | 1500 | × | 6 5 | − | 2000 | × | 6 5 | − | 2520 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 10 100 | − | 1410 | ) | × | 12 |
| = | 6 5 | X | − | 6000 | − | 1800 | − | 2400 | − | 2520 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 10 100 | − | 1410 | ) | × | 12 |
| = | 6 5 | X | − | 12720 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 10 100 | − | 1410 | ) | × | 12 |
| = | 6 5 | X | − | 12720 | − | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 10 100 | × | 12 | + | 1410 | × | 12 |
| = | 6 5 | X | − | 12720 | − | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 6 5 | + | 16920 |
| = | 6 5 | X | + | 4200 | − | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 6 5 |
| = | 6 5 | X | + | 4200 | − | X | × | 6 5 | + | ( | 5000 | + | 1500 | + | 2000 | ) | × | 6 5 |
| = | 0 | X | + | 4200 | + | ( | 5000 | + | 1500 | + | 2000 | ) | × | 6 5 |
| = | 0 | X | + | 4200 | + | 5000 | × | 6 5 | + | 1500 | × | 6 5 | + | 2000 | × | 6 5 |
| = | 0 | X | + | 4200 | + | 6000 | + | 1800 | + | 2400 |
| = | 0 | X | + | 14400 |
| 0 | X | + | 14400 | = | 4000 |
| = | 4000 | − | 14400 |