8 100 | x | − | ( | 30000 | − | x | ) | × | 3 100 | = | 1300 |
| Left side of the equation = | 8 100 | x | − | 30000 | × | 3 100 | + | x | × | 3 100 |
| = | 8 100 | x | − | 900 | + | x | × | 3 100 |
| = | 11 100 | x | − | 900 |
11 100 | x | − | 900 | = | 1300 |
11 100 | x | = | 1300 | + | 900 |
11 100 | x | = | 2200 |
| x | = | 2200 | ÷ | 11 100 |
| = | 2200 | × | 100 11 |
| = | 200 | × | 100 |
| x | = | 20000 |