| ( | x | x | − | 4 | x | + | 7 | ) | ( | x | x | + | 3 | ) | = | 12 |
| Left side of the equation = | x | x | ( | x | x | + | 3 | ) | − | 4 | x | ( | x | x | + | 3 | ) | + | 7 | ( | x | x | + | 3 | ) |
| = | x | x | x | x | + | x | x | × | 3 | − | 4 | x | ( | x | x | + | 3 | ) | + | 7 | ( | x | x | + | 3 | ) |
| = | x | x | x | x | + | x | x | × | 3 | − | 4 | x | x | x | − | 4 |
| = | x | x | x | x | + | x | x | × | 3 | − | 4 | x | x | x | − | 12 |
| = | x | x | x | x | + | x | x | × | 3 | − | 4 | x | x | x | − | 12 |
| = | x | x | x | x | + | x | x | × | 3 | − | 4 | x | x | x | − | 12 |
| x | x | x | x | + | x | x | × | 3 | − | 4 | x | x | x | − | 12 | = | 12 |