| ( | 7 | x | + | 5 | ) | ( | 5 | x | + | 5 | ) | = | 13 | ÷ | 10 |
| 方程左边 = | 7 | x | ( | 5 | x | + | 5 | ) | + | 5 | ( | 5 | x | + | 5 | ) |
| = | 7 | x | × | 5 | x | + | 7 | x | × | 5 | + | 5 | ( | 5 | x | + | 5 | ) |
| = | 35 | x | x | + | 35 | x | + | 5 | ( | 5 | x | + | 5 | ) |
| = | 35 | x | x | + | 35 | x | + | 5 | × | 5 | x | + | 5 | × | 5 |
| = | 35 | x | x | + | 35 | x | + | 25 | x | + | 25 |
| = | 35 | x | x | + | 60 | x | + | 25 |
| 35 | x | x | + | 60 | x | + | 25 | = | 13 | ÷ | 10 |
| 方程右边 = | 13 10 |
| 35 | x | x | + | 60 | x | + | 25 | = | 13 10 |