| ( | 12 | − | 10 | ) | x | + | ( | 23 | − | 15 | ) | ( | 100 | − | x | ) | = | 1300 |
| Left side of the equation = | 12 | x | − | 10 | x | + | ( | 23 | − | 15 | ) | ( | 100 | − | x | ) |
| = | 2 | x | + | ( | 23 | − | 15 | ) | ( | 100 | − | x | ) |
| = | 2 | x | + | 23 | ( | 100 | − | x | ) | − | 15 | ( | 100 | − | x | ) |
| = | 2 | x | + | 23 | × | 100 | − | 23 | x | − | 15 | ( | 100 | − | x | ) |
| = | 2 | x | + | 2300 | − | 23 | x | − | 15 | ( | 100 | − | x | ) |
| = | - | 21 | x | + | 2300 | − | 15 | ( | 100 | − | x | ) |
| = | - | 21 | x | + | 2300 | − | 15 | × | 100 | + | 15 | x |
| = | - | 21 | x | + | 2300 | − | 1500 | + | 15 | x |
| = | - | 6 | x | + | 800 |
| - | 6 | x | + | 800 | = | 1300 |
| - | 6 | x | = | 1300 | − | 800 |
| - | 6 | x | = | 500 |
| - | 500 | = | 6 | x |
| 6 | x | = | - | 500 |
| x | = | - | 500 | ÷ | 6 |
| = | - | 500 | × | 1 6 |
| = | - | 250 | × | 1 3 |
| x | = | - | 250 3 |
| x | = | - 83.333333 |