| 1 | ÷ | u | + | 1 | ÷ | ( | 220 | − | u | ) | = | 1 | ÷ | 56 |
| 方程两边同时乘以: | u |
| 1 | + | 1 | ÷ | ( | 220 | − | u | ) | × | u | = | 1 | ÷ | 56 | × | u |
| 方程两边同时乘以: | ( | 220 | − | u | ) |
| 1 | ( | 220 | − | u | ) | + | 1 | u | = | 1 | ÷ | 56 | × | u | ( | 220 | − | u | ) |
| 1 | × | 220 | − | 1 | u | + | 1 | u | = | 1 | ÷ | 56 | × | u | ( | 220 | − | u | ) |
| 1 | × | 220 | − | 1 | u | + | 1 | u | = | 1 | ÷ | 56 | × | u | × | 220 | − | 1 | ÷ | 56 | × | u | u |
| 220 | − | 1 | u | + | 1 | u | = | 55 14 | u | − | 1 56 | u | u |
| 220 | − | 0 | u | = | 55 14 | u | − | 1 56 | u | u |