| ( | x | + | 10 | ) | ( | x | + | 10 | ) | ( | x | + | 10 | ) | = | - | 125 |
| 方程左边 = | x | ( | x | + | 10 | ) | ( | x | + | 10 | ) | + | 10 | ( | x | + | 10 | ) | ( | x | + | 10 | ) |
| = | x | x | ( | x | + | 10 | ) | + | x | × | 10 | ( | x | + | 10 | ) | + | 10 | ( | x | + | 10 | ) | ( | x | + | 10 | ) |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | ( | x | + | 10 | ) | + | 10 | ( | x | + | 10 | ) | ( | x | + | 10 | ) |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | x | × | 10 | × | 10 |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | x | × | 100 | + | 10 |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | 100 | x | + | 10 |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | 100 | x | + | 10 |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | 100 | x | + | 10 |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | 100 | x | + | 10 |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | 200 | x | + | 10 |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | 200 | x | + | 10 |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | 200 | x | + | 10 |
| = | x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | 300 | x | + | 10 |
| x | x | x | + | x | x | × | 10 | + | x | × | 10 | x | + | 300 | x | + | 10 | = | - | 125 |