| ( | x | − | 12 | ) | ( | 60 | + | 8 | ( | 20 | − | x | ) | ÷ | 2 | ) | = | 432 |
| 方程左边 = | x | ( | 60 | + | 8 | ( | 20 | − | x | ) | ÷ | 2 | ) | − | 12 | ( | 60 | + | 8 | ( | 20 | − | x | ) | ÷ | 2 | ) |
| = | x | × | 60 | + | x | × | 8 | ( | 20 | − | x | ) | ÷ | 2 | − | 12 | ( | 60 | + | 8 | ( | 20 | − | x | ) | ÷ | 2 | ) |
| = | x | × | 60 | + | x | × | 4 | ( | 20 | − | x | ) | − | 12 | ( | 60 | + | 8 | ( | 20 | − | x | ) | ÷ | 2 | ) |
| = | 60 | x | + | x | × | 4 | × | 20 | − | x | × | 4 | x | − | 12 | ( | 60 | + | 8 | ( | 20 | − | x | ) | ÷ | 2 | ) |
| = | 60 | x | + | x | × | 80 | − | x | × | 4 | x | − | 12 | ( | 60 | + | 8 | ( | 20 | − | x | ) | ÷ | 2 | ) |
| = | 140 | x | − | x | × | 4 | x | − | 12 | ( | 60 | + | 8 | ( | 20 | − | x | ) | ÷ | 2 | ) |
| = | 140 | x | − | x | × | 4 | x | − | 12 | × | 60 | − | 12 | × | 8 | ( | 20 | − | x | ) | ÷ | 2 |
| = | 140 | x | − | x | × | 4 | x | − | 720 | − | 48 | ( | 20 | − | x | ) |
| = | 140 | x | − | x | × | 4 | x | − | 720 | − | 48 | × | 20 | + | 48 | x |
| = | 140 | x | − | x | × | 4 | x | − | 720 | − | 960 | + | 48 | x |
| = | 188 | x | − | x | × | 4 | x | − | 1680 |
| 188 | x | − | x | × | 4 | x | − | 1680 | = | 432 |