| 4 | ( | 87 | ÷ | ( | 2 | x | + | 9 | ) | + | 1 | ) | + | 1 | = | - | 7 |
| 4 | × | 87 | ÷ | ( | 2 | x | + | 9 | ) | + | 4 | × | 1 | + | 1 | = | - | 7 |
| 348 | ÷ | ( | 2 | x | + | 9 | ) | + | 4 | + | 1 | = | - | 7 |
| 348 | ÷ | ( | 2 | x | + | 9 | ) | + | 5 | = | - | 7 |
| 方程两边同时乘以: | ( | 2 | x | + | 9 | ) |
| 348 | + | 5 | ( | 2 | x | + | 9 | ) | = | - | 7 | ( | 2 | x | + | 9 | ) |
| 348 | + | 5 | × | 2 | x | + | 5 | × | 9 | = | - | 7 | ( | 2 | x | + | 9 | ) |
| 348 | + | 5 | × | 2 | x | + | 5 | × | 9 | = | - | 7 | × | 2 | x | − | 7 | × | 9 |
| 348 | + | 10 | x | + | 45 | = | - | 14 | x | − | 63 |
| 393 | + | 10 | x | = | - | 14 | x | − | 63 |
| 10 | x | + | 14 | x | = | - | 63 | − | 393 |
| 24 | x | = | - | 63 | − | 393 |
| 24 | x | = | - | 456 |
| x | = | - | 456 | ÷ | 24 |
| = | - | 456 | × | 1 24 |
| = | - | 19 | × | 1 |
| x | = | - | 19 |