| ( | 40 | + | X | ) | ÷ | ( | 40 | + | 4 | X | ) | = | 2 | ÷ | 3 |
| 方程两边同时乘以: | ( | 40 | + | 4 | X | ) |
| ( | 40 | + | X | ) | = | 2 | ÷ | 3 | × | ( | 40 | + | 4 | X | ) |
| 40 | + | X | = | 2 | ÷ | 3 | × | ( | 40 | + | 4 | X | ) |
| 40 | + | X | = | 2 | ÷ | 3 | × | 40 | + | 2 | ÷ | 3 | × | 4 | X |
| 40 | + | X | = | 80 3 | + | 8 3 | X |
| X | − | 8 3 | X | = | 80 3 | − | 40 |
| - | 5 3 | X | = | 80 3 | − | 40 |
| - | 5 3 | X | = | - | 40 3 |
40 3 | = | 5 3 | X |
5 3 | X | = | 40 3 |
| X | = | 40 3 | ÷ | 5 3 |
| = | 40 3 | × | 3 5 |
| = | 8 | × | 1 |
| X | = | 8 |