| 80 | × | 9 10 | x | = | 80 | × | 60 | + | ( | x | − | 60 | ) | × | 4 5 |
| 方程左边 = | 72 | x |
| 72 | x | = | 80 | × | 60 | + | ( | x | − | 60 | ) | × | 4 5 |
| 方程右边 = | 4800 | + | ( | x | − | 60 | ) | × | 4 5 |
| 72 | x | = | 4800 | + | ( | x | − | 60 | ) | × | 4 5 |
| 方程右边 = | 4800 | + | x | × | 4 5 | − | 60 | × | 4 5 |
| = | 4800 | + | x | × | 4 5 | − | 48 |
| = | 4752 | + | 4 5 | x |
| 72 | x | = | 4752 | + | 4 5 | x |
| 72 | x | − | 4 5 | x | = | 4752 |
356 5 | x | = | 4752 |
| x | = | 4752 | ÷ | 356 5 |
| = | 4752 | × | 5 356 |
| = | 1188 | × | 5 89 |
| x | = | 5940 89 |
| x | = | 66.741573 |