| ( | 80 100 | x | − | ( | x | − | 50 | ) | ) | × | 10 | = | 20 | × | 12 |
| Left side of the equation = | 80 100 | x | × | 10 | − | ( | x | − | 50 | ) | × | 10 |
| = | 8 | x | − | ( | x | − | 50 | ) | × | 10 |
| = | 8 | x | − | x | × | 10 | + | 50 | × | 10 |
| = | 8 | x | − | x | × | 10 | + | 500 |
| = | - | 2 | x | + | 500 |
| - | 2 | x | + | 500 | = | 20 | × | 12 |
| Right side of the equation = | 240 |
| - | 2 | x | + | 500 | = | 240 |
| - | 2 | x | = | 240 | − | 500 |
| - | 2 | x | = | - | 260 |
| 260 | = | 2 | x |
| 2 | x | = | 260 |
| x | = | 260 | ÷ | 2 |
| = | 260 | × | 1 2 |
| = | 130 | × | 1 |
| x | = | 130 |