| 12 | ( | 2 | − | 5 | ( | 2 | x | + | 2 | ) | ) | − | 5 | ( | 2 | ( | 3 | − | 10 | x | ) | − | 30 | ) | = | 16 |
| 方程左边 = | 12 | × | 2 | − | 12 | × | 5 | ( | 2 | x | + | 2 | ) | − | 5 | ( | 2 | ( | 3 | − | 10 | x | ) | − | 30 | ) |
| = | 24 | − | 60 | ( | 2 | x | + | 2 | ) | − | 5 | ( | 2 | ( | 3 | − | 10 | x | ) | − | 30 | ) |
| = | 24 | − | 60 | × | 2 | x | − | 60 | × | 2 | − | 5 | ( | 2 | ( | 3 | − | 10 | x | ) | − | 30 | ) |
| = | 24 | − | 120 | x | − | 120 | − | 5 | ( | 2 | ( | 3 | − | 10 | x | ) | − | 30 | ) |
| = | - | 96 | − | 120 | x | − | 5 | ( | 2 | ( | 3 | − | 10 | x | ) | − | 30 | ) |
| = | - | 96 | − | 120 | x | − | 5 | × | 2 | ( | 3 | − | 10 | x | ) | + | 5 | × | 30 |
| = | - | 96 | − | 120 | x | − | 10 | ( | 3 | − | 10 | x | ) | + | 150 |
| = | 54 | − | 120 | x | − | 10 | ( | 3 | − | 10 | x | ) |
| = | 54 | − | 120 | x | − | 10 | × | 3 | + | 10 | × | 10 | x |
| = | 54 | − | 120 | x | − | 30 | + | 100 | x |
| = | 24 | − | 20 | x |
| 24 | − | 20 | x | = | 16 |
| - | 20 | x | = | 16 | − | 24 |
| - | 20 | x | = | - | 8 |
| 8 | = | 20 | x |
| 20 | x | = | 8 |
| x | = | 8 | ÷ | 20 |
| = | 8 | × | 1 20 |
| = | 2 | × | 1 5 |
| x | = | 2 5 |
| x | = | 0.4 |