| 1200 | × | 6 | x | + | 1600 | × | 5 | ( | - | 2 | x | + | 20 | ) | + | 1000 | × | 4 | ( | 20 | − | x | − | ( | - | 2 | x | + | 20 | ) | ) | = | 0 |
| Left side of the equation = | 7200 | x | + | 8000 | ( | - | 2 | x | + | 20 | ) | + | 4000 | ( | 20 | − | x | − | ( | - | 2 | x | + | 20 | ) | ) |
| 7200 | x | + | 8000 | ( | - | 2 | x | + | 20 | ) | + | 4000 | ( | 20 | − | x | − | ( | - | 2 | x | + | 20 | ) | ) | = | 0 |
| Left side of the equation = | 7200 | x | − | 8000 | × | 2 | x | + | 8000 | × | 20 | + | 4000 | ( | 20 | − | x | − | ( | - | 2 | x | + | 20 | ) | ) |
| = | 7200 | x | − | 16000 | x | + | 160000 | + | 4000 | ( | 20 | − | x | − | ( | - | 2 | x | + | 20 | ) | ) |
| = | - | 8800 | x | + | 160000 | + | 4000 | ( | 20 | − | x | − | ( | - | 2 | x | + | 20 | ) | ) |
| = | - | 8800 | x | + | 160000 | + | 4000 | × | 20 | − | 4000 | x | − | 4000 | ( | - | 2 | x | + | 20 | ) |
| = | - | 8800 | x | + | 160000 | + | 80000 | − | 4000 | x | − | 4000 | ( | - | 2 | x | + | 20 | ) |
| = | - | 12800 | x | + | 240000 | − | 4000 | ( | - | 2 | x | + | 20 | ) |
| = | - | 12800 | x | + | 240000 | + | 4000 | × | 2 | x | − | 4000 | × | 20 |
| = | - | 12800 | x | + | 240000 | + | 8000 | x | − | 80000 |
| = | - | 4800 | x | + | 160000 |
| - | 4800 | x | + | 160000 | = | 0 |
| - | 4800 | x | = | 0 | − | 160000 |
| - | 4800 | x | = | - | 160000 |
| 160000 | = | 4800 | x |
| 4800 | x | = | 160000 |
| x | = | 160000 | ÷ | 4800 |
| = | 160000 | × | 1 4800 |
| = | 100 | × | 1 3 |
| x | = | 100 3 |
| x | = | 33.333333 |