| ( | 100 | − | 60 | − | x | ) | ( | 40 | + | 2 | x | ) | = | 1750 |
| 方程左边 = | 100 | ( | 40 | + | 2 | x | ) | − | 60 | ( | 40 | + | 2 | x | ) | − | x | ( | 40 | + | 2 | x | ) |
| = | 100 | × | 40 | + | 100 | × | 2 | x | − | 60 | ( | 40 | + | 2 | x | ) | − | x | ( | 40 | + | 2 | x | ) |
| = | 4000 | + | 200 | x | − | 60 | ( | 40 | + | 2 | x | ) | − | x | ( | 40 | + | 2 | x | ) |
| = | 4000 | + | 200 | x | − | 60 | × | 40 | − | 60 | × | 2 | x | − | x | ( | 40 | + | 2 | x | ) |
| = | 4000 | + | 200 | x | − | 2400 | − | 120 | x | − | x | ( | 40 | + | 2 | x | ) |
| = | 1600 | + | 80 | x | − | x | ( | 40 | + | 2 | x | ) |
| = | 1600 | + | 80 | x | − | x | × | 40 | − | x | × | 2 | x |
| = | 1600 | + | 40 | x | − | x | × | 2 | x |
| 1600 | + | 40 | x | − | x | × | 2 | x | = | 1750 |