| ( | 4 | x | + | 24 | ) | ( | 60 | − | 5 | x | ) | = | 1540 |
| 方程左边 = | 4 | x | ( | 60 | − | 5 | x | ) | + | 24 | ( | 60 | − | 5 | x | ) |
| = | 4 | x | × | 60 | − | 4 | x | × | 5 | x | + | 24 | ( | 60 | − | 5 | x | ) |
| = | 240 | x | − | 20 | x | x | + | 24 | ( | 60 | − | 5 | x | ) |
| = | 240 | x | − | 20 | x | x | + | 24 | × | 60 | − | 24 | × | 5 | x |
| = | 240 | x | − | 20 | x | x | + | 1440 | − | 120 | x |
| = | 120 | x | − | 20 | x | x | + | 1440 |
| 120 | x | − | 20 | x | x | + | 1440 | = | 1540 |