| - | 6 | + | 12 | ( | 8 | + | 5 | ( | 7 | + | x | ) | ) | = | 10 | ( | - | 3 | x | + | 6 | ) |
| Left side of the equation = | - | 6 | + | 12 | × | 8 | + | 12 | × | 5 | ( | 7 | + | x | ) |
| = | - | 6 | + | 96 | + | 60 | ( | 7 | + | x | ) |
| = | 90 | + | 60 | ( | 7 | + | x | ) |
| = | 90 | + | 60 | × | 7 | + | 60 | x |
| = | 90 | + | 420 | + | 60 | x |
| = | 510 | + | 60 | x |
| 510 | + | 60 | x | = | 10 | ( | - | 3 | x | + | 6 | ) |
| Right side of the equation = | - | 10 | × | 3 | x | + | 10 | × | 6 |
| = | - | 30 | x | + | 60 |
| 510 | + | 60 | x | = | - | 30 | x | + | 60 |
| 60 | x | + | 30 | x | = | 60 | − | 510 |
| 90 | x | = | 60 | − | 510 |
| 90 | x | = | - | 450 |
| x | = | - | 450 | ÷ | 90 |
| = | - | 450 | × | 1 90 |
| = | - | 5 | × | 1 |
| x | = | - | 5 |