| ( | 8 | + | x | ) | ( | 12 | + | x | + | 1 | ) | = | 180 |
| 方程左边 = | 8 | ( | 12 | + | x | + | 1 | ) | + | x | ( | 12 | + | x | + | 1 | ) |
| = | 8 | × | 12 | + | 8 | x | + | 8 | × | 1 | + | x | ( | 12 | + | x | + | 1 | ) |
| = | 96 | + | 8 | x | + | 8 | + | x | ( | 12 | + | x | + | 1 | ) |
| = | 104 | + | 8 | x | + | x | ( | 12 | + | x | + | 1 | ) |
| = | 104 | + | 8 | x | + | x | × | 12 | + | x | x | + | x | × | 1 |
| = | 104 | + | 21 | x | + | x | x |
| 104 | + | 21 | x | + | x | x | = | 180 |