| 68 | × | 100 | ÷ | X | ÷ | 21 20 | ÷ | 90 | × | 100 | = | 101 |
| 方程两边同时乘以: | X |
| 68 | × | 100 | ÷ | 21 20 | ÷ | 90 | × | 100 | = | 101 | X |
| - | 101 | X | = | - | 68 | × | 100 | ÷ | 21 20 | ÷ | 90 | × | 100 |
| - | 101 | X | = | - | 1360000 189 |
1360000 189 | = | 101 | X |
| 101 | X | = | 1360000 189 |
| X | = | 1360000 189 | ÷ | 101 |
| = | 1360000 189 | × | 1 101 |
| X | = | 1360000 19089 |
| X | = | 71.24522 |