| 40 | × | 30 | + | ( | 60 | − | x | ) | × | 20 | + | 10 | x | = | 2200 |
| Left side of the equation = | 1200 | + | ( | 60 | − | x | ) | × | 20 | + | 10 | x |
| 1200 | + | ( | 60 | − | x | ) | × | 20 | + | 10 | x | = | 2200 |
| Left side of the equation = | 1200 | + | 60 | × | 20 | − | x | × | 20 | + | 10 | x |
| = | 1200 | + | 1200 | − | x | × | 20 | + | 10 | x |
| = | 2400 | − | 10 | x |
| 2400 | − | 10 | x | = | 2200 |
| - | 10 | x | = | 2200 | − | 2400 |
| - | 10 | x | = | - | 200 |
| 200 | = | 10 | x |
| 10 | x | = | 200 |
| x | = | 200 | ÷ | 10 |
| = | 200 | × | 1 10 |
| = | 20 | × | 1 |
| x | = | 20 |