| ( | 40 | − | x | ) | ( | 16 | − | 4 | ÷ | 5 | × | x | ) | = | 720 |
| Left side of the equation = | 40 | ( | 16 | − | 4 | ÷ | 5 | × | x | ) | − | x | ( | 16 | − | 4 | ÷ | 5 | × | x | ) |
| = | 40 | × | 16 | − | 40 | × | 4 | ÷ | 5 | × | x | − | x | ( | 16 | − | 4 | ÷ | 5 | × | x | ) |
| = | 640 | − | 32 | x | − | x | ( | 16 | − | 4 | ÷ | 5 | × | x | ) |
| = | 640 | − | 32 | x | − | x | × | 16 | + | x | × | 4 | ÷ | 5 | × | x |
| = | 640 | − | 32 | x | − | x | × | 16 | + | x | × | 4 5 | x |
| = | 640 | − | 48 | x | + | x | × | 4 5 | x |
| 640 | − | 48 | x | + | x | × | 4 5 | x | = | 720 |