| ( | 40 | − | 3 | x | ) | ( | 30 | + | 6 | x | ) | = | 1600 |
| Left side of the equation = | 40 | ( | 30 | + | 6 | x | ) | − | 3 | x | ( | 30 | + | 6 | x | ) |
| = | 40 | × | 30 | + | 40 | × | 6 | x | − | 3 | x | ( | 30 | + | 6 | x | ) |
| = | 1200 | + | 240 | x | − | 3 | x | ( | 30 | + | 6 | x | ) |
| = | 1200 | + | 240 | x | − | 3 | x | × | 30 | − | 3 | x | × | 6 | x |
| = | 1200 | + | 240 | x | − | 90 | x | − | 18 | x | x |
| = | 1200 | + | 150 | x | − | 18 | x | x |
| 1200 | + | 150 | x | − | 18 | x | x | = | 1600 |