| 40 | × | 80 | ÷ | x | = | 72 | ÷ | x | + | 5 | × | 50 |
| 方程两边同时乘以: | x |
| 40 | × | 80 | = | 72 | ÷ | 1 | × | 1 | + | 5 | × | 50 | x |
| - | 5 | × | 50 | x | = | 72 | ÷ | 1 | × | 1 | − | 40 | × | 80 |
| - | 250 | x | = | 72 | ÷ | 1 | × | 1 | − | 40 | × | 80 |
| - | 250 | x | = | 72 | − | 3200 |
| - | 250 | x | = | - | 3128 |
| 3128 | = | 250 | x |
| 250 | x | = | 3128 |
| x | = | 3128 | ÷ | 250 |
| = | 3128 | × | 1 250 |
| = | 1564 | × | 1 125 |
| x | = | 1564 125 |
| x | = | 12.512 |