| ( | 1000 | − | x | ) | × | 7 | = | ( | 800 | − | x | ) | × | 8 |
| Left side of the equation = | 1000 | × | 7 | − | x | × | 7 |
| = | 7000 | − | x | × | 7 |
| 7000 | − | 7 | x | = | ( | 800 | − | x | ) | × | 8 |
| Right side of the equation = | 800 | × | 8 | − | x | × | 8 |
| = | 6400 | − | x | × | 8 |
| 7000 | − | 7 | x | = | 6400 | − | 8 | x |
| - | 7 | x | + | 8 | x | = | 6400 | − | 7000 |
| x | = | 6400 | − | 7000 |
| x | = | 6400 | − | 7000 |
| x | = | - | 600 |