21 5 | x | + | 21 5 | ( | x | − | 18 | ) | = | 567 |
| Left side of the equation = | 21 5 | x | + | 21 5 | x | − | 21 5 | × | 18 |
| = | 21 5 | x | + | 21 5 | x | − | 378 5 |
| = | 42 5 | x | − | 378 5 |
42 5 | x | − | 378 5 | = | 567 |
42 5 | x | = | 567 | + | 378 5 |
42 5 | x | = | 3213 5 |
| x | = | 3213 5 | ÷ | 42 5 |
| = | 3213 5 | × | 5 42 |
| = | 153 | × | 1 2 |
| x | = | 153 2 |
| x | = | 76.5 |