| ( | 44 | + | x | − | 40 | ) | ( | 300 | − | 10 | x | ) | = | 2640 |
| Left side of the equation = | 44 | ( | 300 | − | 10 | x | ) | + | x | ( | 300 | − | 10 | x | ) | − | 40 | ( | 300 | − | 10 | x | ) |
| = | 44 | × | 300 | − | 44 | × | 10 | x | + | x | ( | 300 | − | 10 | x | ) | − | 40 | ( | 300 | − | 10 | x | ) |
| = | 13200 | − | 440 | x | + | x | ( | 300 | − | 10 | x | ) | − | 40 | ( | 300 | − | 10 | x | ) |
| = | 13200 | − | 440 | x | + | x | × | 300 | − | x | × | 10 | x | − | 40 | ( | 300 | − | 10 | x | ) |
| = | 13200 | − | 140 | x | − | x | × | 10 | x | − | 40 | ( | 300 | − | 10 | x | ) |
| = | 13200 | − | 140 | x | − | x | × | 10 | x | − | 40 | × | 300 | + | 40 | × | 10 | x |
| = | 13200 | − | 140 | x | − | x | × | 10 | x | − | 12000 | + | 400 | x |
| = | 1200 | + | 260 | x | − | x | × | 10 | x |
| 1200 | + | 260 | x | − | x | × | 10 | x | = | 2640 |