| ( | 60 | + | x | − | 40 | ) | ( | 10 | x | + | 100 | ) | = | 2090 |
| Left side of the equation = | 60 | ( | 10 | x | + | 100 | ) | + | x | ( | 10 | x | + | 100 | ) | − | 40 | ( | 10 | x | + | 100 | ) |
| = | 60 | × | 10 | x | + | 60 | × | 100 | + | x | ( | 10 | x | + | 100 | ) | − | 40 | ( | 10 | x | + | 100 | ) |
| = | 600 | x | + | 6000 | + | x | ( | 10 | x | + | 100 | ) | − | 40 | ( | 10 | x | + | 100 | ) |
| = | 600 | x | + | 6000 | + | x | × | 10 | x | + | x | × | 100 | − | 40 | ( | 10 | x | + | 100 | ) |
| = | 700 | x | + | 6000 | + | x | × | 10 | x | − | 40 | ( | 10 | x | + | 100 | ) |
| = | 700 | x | + | 6000 | + | x | × | 10 | x | − | 40 | × | 10 | x | − | 40 | × | 100 |
| = | 700 | x | + | 6000 | + | x | × | 10 | x | − | 400 | x | − | 4000 |
| = | 300 | x | + | 2000 | + | x | × | 10 | x |
| 300 | x | + | 2000 | + | x | × | 10 | x | = | 2090 |