| ( | 20 | + | 2 | x | ) | ( | 8 | + | 2 | x | ) | − | 20 | × | 8 | = | 1 | ÷ | 4 | × | 20 | × | 8 |
| 方程左边 = | ( | 20 | + | 2 | x | ) | ( | 8 | + | 2 | x | ) | − | 160 |
| ( | 20 | + | 2 | x | ) | ( | 8 | + | 2 | x | ) | − | 160 | = | 1 | ÷ | 4 | × | 20 | × | 8 |
| 方程左边 = | 20 | ( | 8 | + | 2 | x | ) | + | 2 | x | ( | 8 | + | 2 | x | ) | − | 160 |
| = | 20 | × | 8 | + | 20 | × | 2 | x | + | 2 | x | ( | 8 | + | 2 | x | ) | − | 160 |
| = | 160 | + | 40 | x | + | 2 | x | ( | 8 | + | 2 | x | ) | − | 160 |
| = | 0 | + | 40 | x | + | 2 | x | ( | 8 | + | 2 | x | ) |
| = | 40 | x | + | 2 | x | × | 8 | + | 2 | x | × | 2 | x |
| = | 40 | x | + | 16 | x | + | 4 | x | x |
| = | 56 | x | + | 4 | x | x |
| 56 | x | + | 4 | x | x | = | 1 | ÷ | 4 | × | 20 | × | 8 |
| 方程右边 = | 40 |
| 56 | x | + | 4 | x | x | = | 40 |