| 800 | = | 400 | ÷ | 1 | + | r | + | 300 | ÷ | ( | 1 | + | r | ) | × | 2 | + | ( | 1 | + | r | ) | × | 3 |
| 方程两边同时乘以: | ( | 1 | + | r | ) |
| 800 | ( | 1 | + | r | ) | = | 400 | ÷ | 1 | × | ( | 1 | + | r | ) | + | r | ( | 1 | + | r | ) | + | 300 | × | 2 | + | ( | 1 | + | r | ) | × | 3 | ( | 1 | + | r | ) |
| 800 | × | 1 | + | 800 | r | = | 400 | ÷ | 1 | × | ( | 1 | + | r | ) | + | r | ( | 1 | + | r | ) | + | 300 | × | 2 | + | ( | 1 | + | r | ) | × | 3 | ( | 1 | + | r | ) |
| 800 | × | 1 | + | 800 | r | = | 400 | ÷ | 1 | × | 1 | + | 400 | ÷ | 1 | × | r | + | r | ( | 1 | + | r | ) | + | 300 | × | 2 | + | ( | 1 | + | r | ) | × | 3 |
| 800 | + | 800 | r | = | 400 | + | 400 | r | + | r | ( | 1 | + | r | ) | + | 600 | + | ( | 1 | + | r | ) | × | 3 | ( | 1 | + | r | ) |
| 800 | + | 800 | r | = | 1000 | + | 400 | r | + | r | ( | 1 | + | r | ) | + | ( | 1 | + | r | ) | × | 3 | ( | 1 | + | r | ) |
| 800 | + | 800 | r | = | 1000 | + | 400 | r | + | r | × | 1 | + | r | r | + | ( | 1 | + | r | ) | × | 3 | ( | 1 | + | r | ) |
| 800 | + | 800 | r | = | 1000 | + | 401 | r | + | r | r | + | ( | 1 | + | r | ) | × | 3 | ( | 1 | + | r | ) |
| 800 | + | 800 | r | = | 1000 | + | 401 | r | + | r | r | + | 1 | × | 3 | ( | 1 | + | r | ) | + | r | × | 3 | ( | 1 | + | r | ) |
| 800 | + | 800 | r | = | 1000 | + | 401 | r | + | r | r | + | 3 | ( | 1 | + | r | ) | + | r | × | 3 | ( | 1 | + | r | ) |
| 800 | + | 800 | r | = | 1000 | + | 401 | r | + | r | r | + | 3 | × | 1 | + | 3 | r | + | r | × | 3 | ( | 1 | + | r | ) |
| 800 | + | 800 | r | = | 1000 | + | 401 | r | + | r | r | + | 3 | + | 3 | r | + | r | × | 3 | ( | 1 | + | r | ) |
| 800 | + | 800 | r | = | 1003 | + | 404 | r | + | r | r | + | r | × | 3 | ( | 1 | + | r | ) |
| 800 | + | 800 | r | = | 1003 | + | 404 | r | + | r | r | + | r | × | 3 | × | 1 | + | r | × | 3 | r |
| 800 | + | 800 | r | = | 1003 | + | 404 | r | + | r | r | + | r | × | 3 | + | r | × | 3 | r |
| 800 | + | 800 | r | = | 1003 | + | 407 | r | + | r | r | + | r | × | 3 | r |