| ( | 320 | + | x | − | 40 | ) | ( | 60 | − | x | ÷ | 20 | ) | = | 20160 |
| Left side of the equation = | 320 | ( | 60 | − | x | ÷ | 20 | ) | + | x | ( | 60 | − | x | ÷ | 20 | ) | − | 40 | ( | 60 | − | x | ÷ | 20 | ) |
| = | 320 | × | 60 | − | 320 | x | ÷ | 20 | + | x | ( | 60 | − | x | ÷ | 20 | ) | − | 40 | ( | 60 | − | x | ÷ | 20 | ) |
| = | 19200 | − | 16 | x | + | x | ( | 60 | − | x | ÷ | 20 | ) | − | 40 | ( | 60 | − | x | ÷ | 20 | ) |
| = | 19200 | − | 16 | x | + | x | × | 60 | − | x | x | ÷ | 20 | − | 40 | ( | 60 | − | x | ÷ | 20 | ) |
| = | 19200 | + | 44 | x | − | x | x | × | 1 20 | − | 40 | ( | 60 | − | x | ÷ | 20 | ) |
| = | 19200 | + | 44 | x | − | x | x | × | 1 20 | − | 40 | × | 60 | + | 40 | x | ÷ | 20 |
| = | 19200 | + | 44 | x | − | x | x | × | 1 20 | − | 2400 | + | 2 | x |
| = | 16800 | + | 46 | x | − | x | x | × | 1 20 |
| 16800 | + | 46 | x | − | x | x | × | 1 20 | = | 20160 |