| 1000 | = | 72000000 | ÷ | ( | ( | P | + | 1 | ) | × | 100 | ) |
| 方程两边同时乘以: | ( | ( | P | + | 1 | ) | × | 100 | ) |
| 1000 | ( | ( | P | + | 1 | ) | × | 100 | ) | = | 72000000 |
| 1000 | ( | P | + | 1 | ) | × | 100 | = | 72000000 |
| 100000 | ( | P | + | 1 | ) | = | 72000000 |
| 100000 | P | + | 100000 | × | 1 | = | 72000000 |
| 100000 | P | + | 100000 | = | 72000000 |
| 100000 | P | = | 72000000 | − | 100000 |
| 100000 | P | = | 71900000 |
| P | = | 71900000 | ÷ | 100000 |
| = | 71900000 | × | 1 100000 |
| = | 719 | × | 1 |
| P | = | 719 |