| ( | x | − | 20 | ) | ( | 50 | − | x | ÷ | 10 | + | 18 | ) | = | 0 |
| Left side of the equation = | x | ( | 50 | − | x | ÷ | 10 | + | 18 | ) | − | 20 | ( | 50 | − | x | ÷ | 10 | + | 18 | ) |
| = | x | × | 50 | − | x | x | ÷ | 10 | + | x | × | 18 | − | 20 | ( | 50 | − | x | ÷ | 10 | + | 18 | ) |
| = | 68 | x | − | x | x | × | 1 10 | − | 20 | ( | 50 | − | x | ÷ | 10 | + | 18 | ) |
| = | 68 | x | − | x | x | × | 1 10 | − | 20 | × | 50 | + | 20 | x | ÷ | 10 | − | 20 | × | 18 |
| = | 68 | x | − | x | x | × | 1 10 | − | 1000 | + | 2 | x | − | 360 |
| = | 70 | x | − | x | x | × | 1 10 | − | 1360 |
| 70 | x | − | x | x | × | 1 10 | − | 1360 | = | 0 |