| x | − | 210 | − | ( | x | − | 210 | ) | × | 20 100 | = | ( | 2 | ÷ | 5 | ) | x |
| Left side of the equation = | x | − | 210 | − | x | × | 20 100 | + | 210 | × | 20 100 |
| = | x | − | 210 | − | x | × | 20 100 | + | 42 |
| = | 4 5 | x | − | 168 |
4 5 | x | − | 168 | = | ( | 2 | ÷ | 5 | ) | x |
| Right side of the equation = | 2 | ÷ | 5 | × | x |
| = | 2 5 | x |
4 5 | x | − | 168 | = | 2 5 | x |
4 5 | x | − | 2 5 | x | = | 168 |
2 5 | x | = | 168 |
| x | = | 168 | ÷ | 2 5 |
| = | 168 | × | 5 2 |
| = | 84 | × | 5 |
| x | = | 420 |