| ( | 7 | + | x | ) | ( | 200 | − | 10 | x | ) | = | 1700 |
| Left side of the equation = | 7 | ( | 200 | − | 10 | x | ) | + | x | ( | 200 | − | 10 | x | ) |
| = | 7 | × | 200 | − | 7 | × | 10 | x | + | x | ( | 200 | − | 10 | x | ) |
| = | 1400 | − | 70 | x | + | x | ( | 200 | − | 10 | x | ) |
| = | 1400 | − | 70 | x | + | x | × | 200 | − | x | × | 10 | x |
| = | 1400 | + | 130 | x | − | x | × | 10 | x |
| 1400 | + | 130 | x | − | x | × | 10 | x | = | 1700 |