| ( | x | − | 40 | ) | ( | - | 10 | x | + | 740 | ) | = | 2400 |
| Left side of the equation = | x | ( | - | 10 | x | + | 740 | ) | − | 40 | ( | - | 10 | x | + | 740 | ) |
| = | - | x | × | 10 | x | + | x | × | 740 | − | 40 | ( | - | 10 | x | + | 740 | ) |
| = | - | x | × | 10 | x | + | 740 | x | + | 40 | × | 10 | x | − | 40 | × | 740 |
| = | - | x | × | 10 | x | + | 740 | x | + | 400 | x | − | 29600 |
| = | - | x | × | 10 | x | + | 1140 | x | − | 29600 |
| - | x | × | 10 | x | + | 1140 | x | − | 29600 | = | 2400 |