| 9 | x | + | 4 | ( | 100 | − | x | ) | = | ( | 10 | x | + | 6 | ( | 100 | − | x | ) | ) | × | 75 100 |
| Left side of the equation = | 9 | x | + | 4 | × | 100 | − | 4 | x |
| = | 9 | x | + | 400 | − | 4 | x |
| = | 5 | x | + | 400 |
| 5 | x | + | 400 | = | ( | 10 | x | + | 6 | ( | 100 | − | x | ) | ) | × | 75 100 |
| Right side of the equation = | 10 | x | × | 75 100 | + | 6 | ( | 100 | − | x | ) | × | 75 100 |
| = | 15 2 | x | + | 9 2 | ( | 100 | − | x | ) |
| = | 15 2 | x | + | 9 2 | × | 100 | − | 9 2 | x |
| = | 15 2 | x | + | 450 | − | 9 2 | x |
| = | 3 | x | + | 450 |
| 5 | x | + | 400 | = | 3 | x | + | 450 |
| 5 | x | − | 3 | x | = | 450 | − | 400 |
| 2 | x | = | 450 | − | 400 |
| 2 | x | = | 50 |
| x | = | 50 | ÷ | 2 |
| = | 50 | × | 1 2 |
| = | 25 | × | 1 |
| x | = | 25 |