| ( | 15 | − | x | ) | ( | 100 | + | 10 | x | ) | = | 1560 |
| Left side of the equation = | 15 | ( | 100 | + | 10 | x | ) | − | x | ( | 100 | + | 10 | x | ) |
| = | 15 | × | 100 | + | 15 | × | 10 | x | − | x | ( | 100 | + | 10 | x | ) |
| = | 1500 | + | 150 | x | − | x | ( | 100 | + | 10 | x | ) |
| = | 1500 | + | 150 | x | − | x | × | 100 | − | x | × | 10 | x |
| = | 1500 | + | 50 | x | − | x | × | 10 | x |
| 1500 | + | 50 | x | − | x | × | 10 | x | = | 1560 |