| 30 | ( | 1 | + | m% | ) | ( | 1 | + | 1 2 | × | m% | ) | = | 66 |
| 方程左边 = | 30 | × | 1 | ( | 1 | + | 1 2 | × | m% | ) | + | 30 | × | m% | ( | 1 | + | 1 2 | × | m% | ) |
| = | 30 | ( | 1 | + | 1 2 | × | m% | ) | + | 3 10 | m | ( | 1 | + | 1 2 | × | m% | ) |
| = | 30 | × | 1 | + | 30 | × | 1 2 | × | m% | + | 3 10 | m | ( | 1 | + | 1 2 | × | m% | ) |
| = | 30 | + | 3 20 | m | + | 3 10 | m | ( | 1 | + | 1 2 | × | m% | ) |
| = | 30 | + | 3 20 | m | + | 3 10 | m | × | 1 | + | 3 10 | m | × | 1 2 | × | m% |
| = | 30 | + | 3 20 | m | + | 3 10 | m | + | 3 2000 | m | m |
| = | 30 | + | 9 20 | m | + | 3 2000 | m | m |
| 30 | + | 9 20 | m | + | 3 2000 | m | m | = | 66 |