67 200 | ( | 375 | + | 195 | − | a | ) | = | 405 4 | + | 663 8 | − | 27 100 | a |
| 方程左边 = | 67 200 | × | 375 | + | 67 200 | × | 195 | − | 67 200 | a |
| = | 1005 8 | + | 2613 40 | − | 67 200 | a |
| = | 3819 20 | − | 67 200 | a |
3819 20 | − | 67 200 | a | = | 405 4 | + | 663 8 | − | 27 100 | a |
| 方程右边 = | 1473 8 | − | 27 100 | a |
3819 20 | − | 67 200 | a | = | 1473 8 | − | 27 100 | a |
| - | 67 200 | a | + | 27 100 | a | = | 1473 8 | − | 3819 20 |
| - | 13 200 | a | = | 1473 8 | − | 3819 20 |
| - | 13 200 | a | = | - | 273 40 |
273 40 | = | 13 200 | a |
13 200 | a | = | 273 40 |
| a | = | 273 40 | ÷ | 13 200 |
| = | 273 40 | × | 200 13 |
| = | 21 | × | 5 |
| a | = | 105 |