| ( | 1 | + | 1 2 | ) | x | × | 9 10 | + | ( | 1 | + | 2 5 | ) | ( | 500 | − | x | ) | × | 9 10 | = | 0 |
| Left side of the equation = | 1 | x | × | 9 10 | + | 1 2 | x | × | 9 10 | + | ( | 1 | + | 2 5 | ) | ( | 500 | − | x | ) | × | 9 10 |
| = | 9 10 | x | + | 9 20 | x | + | ( | 1 | + | 2 5 | ) | ( | 500 | − | x | ) | × | 9 10 |
| = | 27 20 | x | + | ( | 1 | + | 2 5 | ) | ( | 500 | − | x | ) | × | 9 10 |
| = | 27 20 | x | + | 1 | ( | 500 | − | x | ) | × | 9 10 | + | 2 5 | ( | 500 | − | x | ) | × | 9 10 |
| = | 27 20 | x | + | 9 10 | ( | 500 | − | x | ) | + | 9 25 | ( | 500 | − | x | ) |
| = | 27 20 | x | + | 9 10 | × | 500 | − | 9 10 | x | + | 9 25 | ( | 500 | − | x | ) |
| = | 27 20 | x | + | 450 | − | 9 10 | x | + | 9 25 | ( | 500 | − | x | ) |
| = | 9 20 | x | + | 450 | + | 9 25 | ( | 500 | − | x | ) |
| = | 9 20 | x | + | 450 | + | 9 25 | × | 500 | − | 9 25 | x |
| = | 9 20 | x | + | 450 | + | 180 | − | 9 25 | x |
| = | 9 100 | x | + | 630 |
9 100 | x | + | 630 | = | 0 |
9 100 | x | = | 0 | − | 630 |
9 100 | x | = | - | 630 |
| x | = | - | 630 | ÷ | 9 100 |
| = | - | 630 | × | 100 9 |
| = | - | 70 | × | 100 |
| x | = | - | 7000 |