| 90 | + | 900 | + | ( | x | − | 5000 | − | 12000 | ) | × | 1 5 | = | 3290 |
| Left side of the equation = | 990 | + | ( | x | − | 5000 | − | 12000 | ) | × | 1 5 |
| 990 | + | ( | x | − | 5000 | − | 12000 | ) | × | 1 5 | = | 3290 |
| Left side of the equation = | 990 | + | x | × | 1 5 | − | 5000 | × | 1 5 | − | 12000 | × | 1 5 |
| = | 990 | + | x | × | 1 5 | − | 1000 | − | 2400 |
| = | - | 2410 | + | 1 5 | x |
| - | 2410 | + | 1 5 | x | = | 3290 |
1 5 | x | = | 3290 | + | 2410 |
1 5 | x | = | 5700 |
| x | = | 5700 | ÷ | 1 5 |
| = | 5700 | × | 5 |
| x | = | 28500 |