309 1000 | × | 72 | = | ( | - | 1 10 | ) | ( | 72 | − | x | ) | + | 4 5 | x |
| 方程左边 = | 2781 125 |
2781 125 | = | ( | - | 1 10 | ) | ( | 72 | − | x | ) | + | 4 5 | x |
| 方程右边 = | - | 1 10 | ( | 72 | − | x | ) | + | 4 5 | x |
| = | - | 1 10 | × | 72 | + | 1 10 | x | + | 4 5 | x |
| = | - | 36 5 | + | 1 10 | x | + | 4 5 | x |
| = | - | 36 5 | + | 9 10 | x |
2781 125 | = | - | 36 5 | + | 9 10 | x |
| - | 9 10 | x | = | - | 36 5 | − | 2781 125 |
| - | 9 10 | x | = | - | 3681 125 |
3681 125 | = | 9 10 | x |
9 10 | x | = | 3681 125 |
| x | = | 3681 125 | ÷ | 9 10 |
| = | 3681 125 | × | 10 9 |
| = | 409 25 | × | 2 |
| x | = | 818 25 |
| x | = | 32.72 |