| 12 | + | 2 | ( | - | 9 | − | 25 | ÷ | ( | 5 | x | + | 5 | ) | ) | = | - | 4 |
| 12 | − | 2 | × | 9 | − | 2 | × | 25 | ÷ | ( | 5 | x | + | 5 | ) | = | - | 4 |
| 12 | − | 18 | − | 50 | ÷ | ( | 5 | x | + | 5 | ) | = | - | 4 |
| - | 6 | − | 50 | ÷ | ( | 5 | x | + | 5 | ) | = | - | 4 |
| Multiply both sides of the equation by: | ( | 5 | x | + | 5 | ) |
| - | 6 | ( | 5 | x | + | 5 | ) | − | 50 | = | - | 4 | ( | 5 | x | + | 5 | ) |
| - | 6 | × | 5 | x | − | 6 | × | 5 | − | 50 | = | - | 4 | ( | 5 | x | + | 5 | ) |
| - | 6 | × | 5 | x | − | 6 | × | 5 | − | 50 | = | - | 4 | × | 5 | x | − | 4 | × | 5 |
| - | 30 | x | − | 30 | − | 50 | = | - | 20 | x | − | 20 |
| - | 30 | x | − | 80 | = | - | 20 | x | − | 20 |
| - | 30 | x | + | 20 | x | = | - | 20 | + | 80 |
| - | 10 | x | = | - | 20 | + | 80 |
| - | 10 | x | = | 60 |
| - | 60 | = | 10 | x |
| 10 | x | = | - | 60 |
| x | = | - | 60 | ÷ | 10 |
| = | - | 60 | × | 1 10 |
| = | - | 6 | × | 1 |
| x | = | - | 6 |