| ( | ( | X | × | 12 | − | ( | 5000 | + | 1500 | + | 2000 | ) | × | 12 | ) | × | 20 100 | − | 16920 | ) | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 20 100 | − | 1410 | ) | × | 12 | = | - | 4000 |
| 方程左边 = | ( | X | × | 12 | − | ( | 5000 | + | 1500 | + | 2000 | ) | × | 12 | ) | × | 20 100 | − | 16920 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 20 100 | − | 1410 | ) | × | 12 |
| = | X | × | 12 | × | 20 100 | − | ( | 5000 | + | 1500 | + | 2000 | ) | × | 12 | × | 20 100 | − | 16920 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 20 100 | − | 1410 | ) | × | 12 |
| = | X | × | 12 5 | − | ( | 5000 | + | 1500 | + | 2000 | ) | × | 12 5 | − | 16920 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 20 100 | − | 1410 | ) | × | 12 |
| = | 12 5 | X | − | 5000 | × | 12 5 | − | 1500 | × | 12 5 | − | 2000 | × | 12 5 | − | 16920 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 20 100 | − | 1410 | ) | × | 12 |
| = | 12 5 | X | − | 12000 | − | 3600 | − | 4800 | − | 16920 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 20 100 | − | 1410 | ) | × | 12 |
| = | 12 5 | X | − | 37320 | − | ( | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 20 100 | − | 1410 | ) | × | 12 |
| = | 12 5 | X | − | 37320 | − | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 20 100 | × | 12 | + | 1410 | × | 12 |
| = | 12 5 | X | − | 37320 | − | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 12 5 | + | 16920 |
| = | 12 5 | X | − | 20400 | − | ( | X | − | ( | 5000 | + | 1500 | + | 2000 | ) | ) | × | 12 5 |
| = | 12 5 | X | − | 20400 | − | X | × | 12 5 | + | ( | 5000 | + | 1500 | + | 2000 | ) | × | 12 5 |
| = | 0 | X | − | 20400 | + | ( | 5000 | + | 1500 | + | 2000 | ) | × | 12 5 |
| = | - | 20400 | + | 5000 | × | 12 5 | + | 1500 | × | 12 5 | + | 2000 | × | 12 5 |
| = | - | 20400 | + | 12000 | + | 3600 | + | 4800 |
| = | - | 0 |
| - | 0 | = | - | 4000 |
| = | - | 4000 | + | 0 |