| 0 | = | 7 20 | Q | − | ( | 120 | + | 1 5 | Q | ) | − | ( | 7 20 | Q | × | 13 100 | − | ( | 5 | + | 3 200 | Q | ) | − | 140 | ) |
| 方程右边 = | 7 20 | Q | − | 120 | − | 1 5 | Q | − | ( | 7 20 | Q | × | 13 100 | − | ( | 5 | + | 3 200 | Q | ) | − | 140 | ) |
| = | 3 20 | Q | − | 120 | − | ( | 7 20 | Q | × | 13 100 | − | ( | 5 | + | 3 200 | Q | ) | − | 140 | ) |
| = | 3 20 | Q | − | 120 | − | 7 20 | Q | × | 13 100 | + | ( | 5 | + | 3 200 | Q | ) | + | 140 |
| = | 3 20 | Q | − | 120 | − | 91 2000 | Q | + | ( | 5 | + | 3 200 | Q | ) | + | 140 |
| = | 209 2000 | Q | + | 20 | + | ( | 5 | + | 3 200 | Q | ) |
| = | 209 2000 | Q | + | 20 | + | 5 | + | 3 200 | Q |
| = | 239 2000 | Q | + | 25 |
| 0 | = | 239 2000 | Q | + | 25 |
| - | 239 2000 | Q | = | 25 | − | 0 |
| - | 239 2000 | Q | = | 25 |
| - | 25 | = | 239 2000 | Q |
239 2000 | Q | = | - | 25 |
| Q | = | - | 25 | ÷ | 239 2000 |
| = | - | 25 | × | 2000 239 |
| Q | = | - | 50000 239 |
| Q | = | - 209.205021 |