| 9 | x | + | 4 | ( | 100 | − | x | ) | = | ( | 10 | x | + | 6 | ( | 100 | − | x | ) | ) | ( | 1 | − | 1 4 | ) |
| 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 | ) | ) | ( | 1 | − | 1 4 | ) |
| Right side of the equation = | 10 | x | ( | 1 | − | 1 4 | ) | + | 6 | ( | 100 | − | x | ) | ( | 1 | − | 1 4 | ) |
| = | 10 | x | × | 1 | − | 10 | x | × | 1 4 | + | 6 | ( | 100 | − | x | ) | ( | 1 | − | 1 4 | ) |
| = | 10 | x | − | 5 2 | x | + | 6 | ( | 100 | − | x | ) | ( | 1 | − | 1 4 | ) |
| = | 15 2 | x | + | 6 | ( | 100 | − | x | ) | ( | 1 | − | 1 4 | ) |
| = | 15 2 | x | + | 6 | × | 100 | ( | 1 | − | 1 4 | ) | − | 6 | x | ( | 1 | − | 1 4 | ) |
| = | 15 2 | x | + | 600 | ( | 1 | − | 1 4 | ) | − | 6 | x | ( | 1 | − | 1 4 | ) |
| = | 15 2 | x | + | 600 | × | 1 | − | 600 | × | 1 4 | − | 6 | x | ( | 1 | − | 1 4 | ) |
| = | 15 2 | x | + | 600 | − | 150 | − | 6 | x | ( | 1 | − | 1 4 | ) |
| = | 15 2 | x | + | 450 | − | 6 | x | ( | 1 | − | 1 4 | ) |
| = | 15 2 | x | + | 450 | − | 6 | x | × | 1 | + | 6 | x | × | 1 4 |
| = | 15 2 | x | + | 450 | − | 6 | x | + | 3 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 |