| 40 | × | 40 | ( | 3 | − | 2 | x | ) | × | 2 | = | 2 | − | 10 | x | ( | 5 | − | 20 | x | ) | × | 2 |
| Left side of the equation = | 3200 | ( | 3 | − | 2 | x | ) |
| 3200 | ( | 3 | − | 2 | x | ) | = | 2 | − | 10 | x | ( | 5 | − | 20 | x | ) | × | 2 |
| Left side of the equation = | 3200 | × | 3 | − | 3200 | × | 2 | x |
| = | 9600 | − | 6400 | x |
| 9600 | − | 6400 | x | = | 2 | − | 10 | x | ( | 5 | − | 20 | x | ) | × | 2 |
| Right side of the equation = | 2 | − | 20 | x | ( | 5 | − | 20 | x | ) |
| 9600 | − | 6400 | x | = | 2 | − | 20 | x | ( | 5 | − | 20 | x | ) |
| Right side of the equation = | 2 | − | 20 | x | × | 5 | + | 20 | x | × | 20 | x |
| = | 2 | − | 100 | x | + | 400 | x | x |
| 9600 | − | 6400 | x | = | 2 | − | 100 | x | + | 400 | x | x |