| ( | 18 | + | x | ) | × | 40 | = | 18 | × | 10 | + | 450 | x |
| 方程左边 = | 18 | × | 40 | + | x | × | 40 |
| = | 720 | + | x | × | 40 |
| 720 | + | 40 | x | = | 18 | × | 10 | + | 450 | x |
| 方程右边 = | 180 | + | 450 | x |
| 720 | + | 40 | x | = | 180 | + | 450 | x |
| 40 | x | − | 450 | x | = | 180 | − | 720 |
| - | 410 | x | = | 180 | − | 720 |
| - | 410 | x | = | - | 540 |
| 540 | = | 410 | x |
| 410 | x | = | 540 |
| x | = | 540 | ÷ | 410 |
| = | 540 | × | 1 410 |
| = | 54 | × | 1 41 |
| x | = | 54 41 |
| x | = | 1.317073 |