| ( | 30 | − | 25 | ) | x | + | ( | 1200 | − | x | ) | ( | 60 | − | 45 | ) | = | ( | 25 | x | + | 45 | ( | 1200 | − | x | ) | ) | × | 30 100 |
| Left side of the equation = | 30 | x | − | 25 | x | + | ( | 1200 | − | x | ) | ( | 60 | − | 45 | ) |
| = | 5 | x | + | ( | 1200 | − | x | ) | ( | 60 | − | 45 | ) |
| = | 5 | x | + | 1200 | ( | 60 | − | 45 | ) | − | x | ( | 60 | − | 45 | ) |
| = | 5 | x | + | 1200 | × | 60 | − | 1200 | × | 45 | − | x | ( | 60 | − | 45 | ) |
| = | 5 | x | + | 72000 | − | 54000 | − | x | ( | 60 | − | 45 | ) |
| = | 5 | x | + | 18000 | − | x | ( | 60 | − | 45 | ) |
| = | 5 | x | + | 18000 | − | x | × | 60 | + | x | × | 45 |
| = | - | 10 | x | + | 18000 |
| - | 10 | x | + | 18000 | = | ( | 25 | x | + | 45 | ( | 1200 | − | x | ) | ) | × | 30 100 |
| Right side of the equation = | 25 | x | × | 30 100 | + | 45 | ( | 1200 | − | x | ) | × | 30 100 |
| = | 15 2 | x | + | 27 2 | ( | 1200 | − | x | ) |
| = | 15 2 | x | + | 27 2 | × | 1200 | − | 27 2 | x |
| = | 15 2 | x | + | 16200 | − | 27 2 | x |
| = | - | 6 | x | + | 16200 |
| - | 10 | x | + | 18000 | = | - | 6 | x | + | 16200 |
| - | 10 | x | + | 6 | x | = | 16200 | − | 18000 |
| - | 4 | x | = | 16200 | − | 18000 |
| - | 4 | x | = | - | 1800 |
| 1800 | = | 4 | x |
| 4 | x | = | 1800 |
| x | = | 1800 | ÷ | 4 |
| = | 1800 | × | 1 4 |
| = | 450 | × | 1 |
| x | = | 450 |