30 100 | x | + | ( | ( | 100 | − | x | ) | × | 50 100 | ) | = | 4220 |
| Left side of the equation = | 30 100 | x | + | ( | 100 | − | x | ) | × | 50 100 |
| = | 30 100 | x | + | 100 | × | 50 100 | − | x | × | 50 100 |
| = | 30 100 | x | + | 50 | − | x | × | 50 100 |
| = | - | 1 5 | x | + | 50 |
| - | 1 5 | x | + | 50 | = | 4220 |
| - | 1 5 | x | = | 4220 | − | 50 |
| - | 1 5 | x | = | 4170 |
| - | 4170 | = | 1 5 | x |
1 5 | x | = | - | 4170 |
| x | = | - | 4170 | ÷ | 1 5 |
| = | - | 4170 | × | 5 |
| x | = | - | 20850 |