| ( | 50 | + | x | − | 40 | ) | ( | 100 | − | 2 | x | ) | = | 1350 |
| Left side of the equation = | 50 | ( | 100 | − | 2 | x | ) | + | x | ( | 100 | − | 2 | x | ) | − | 40 | ( | 100 | − | 2 | x | ) |
| = | 50 | × | 100 | − | 50 | × | 2 | x | + | x | ( | 100 | − | 2 | x | ) | − | 40 | ( | 100 | − | 2 | x | ) |
| = | 5000 | − | 100 | x | + | x | ( | 100 | − | 2 | x | ) | − | 40 | ( | 100 | − | 2 | x | ) |
| = | 5000 | − | 100 | x | + | x | × | 100 | − | x | × | 2 | x | − | 40 | ( | 100 | − | 2 | x | ) |
| = | 5000 | − | 0 | x | − | x | × | 2 | x | − | 40 | ( | 100 | − | 2 | x | ) |
| = | 5000 | − | 0 | x | − | x | × | 2 | x | − | 40 | × | 100 | + | 40 | × | 2 | x |
| = | 5000 | − | 0 | x | − | x | × | 2 | x | − | 4000 | + | 80 | x |
| = | 1000 | + | 80 | x | − | x | × | 2 | x |
| 1000 | + | 80 | x | − | x | × | 2 | x | = | 1350 |