| ( | x | + | 4 | ) | ( | 500 | − | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 | ) | = | 800 |
| 方程左边 = | x | ( | 500 | − | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 | ) | + | 4 | ( | 500 | − | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 | ) |
| = | x | × | 500 | − | x | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 | + | 4 | ( | 500 | − | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 | ) |
| = | x | × | 500 | − | x | ( | x | − | 4 | ) | × | 100 | + | 4 | ( | 500 | − | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 | ) |
| = | 500 | x | − | x | x | × | 100 | + | x | × | 4 | × | 100 | + | 4 | ( | 500 | − | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 | ) |
| = | 500 | x | − | x | x | × | 100 | + | x | × | 400 | + | 4 | ( | 500 | − | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 | ) |
| = | 900 | x | − | x | x | × | 100 | + | 4 | ( | 500 | − | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 | ) |
| = | 900 | x | − | x | x | × | 100 | + | 4 | × | 500 | − | 4 | ( | x | − | 4 | ) | ÷ | 1 10 | × | 10 |
| = | 900 | x | − | x | x | × | 100 | + | 2000 | − | 400 | ( | x | − | 4 | ) |
| = | 900 | x | − | x | x | × | 100 | + | 2000 | − | 400 | x | + | 400 | × | 4 |
| = | 900 | x | − | x | x | × | 100 | + | 2000 | − | 400 | x | + | 1600 |
| = | 500 | x | − | x | x | × | 100 | + | 3600 |
| 500 | x | − | x | x | × | 100 | + | 3600 | = | 800 |