| 13 | x | + | 13 | × | 50 | + | ( | 104 | − | x | − | 50 | ) | × | 11 | = | 1240 |
| Left side of the equation = | 13 | x | + | 650 | + | ( | 104 | − | x | − | 50 | ) | × | 11 |
| 13 | x | + | 650 | + | ( | 104 | − | x | − | 50 | ) | × | 11 | = | 1240 |
| Left side of the equation = | 13 | x | + | 650 | + | 104 | × | 11 | − | x | × | 11 | − | 50 | × | 11 |
| = | 13 | x | + | 650 | + | 1144 | − | x | × | 11 | − | 550 |
| = | 2 | x | + | 1244 |
| 2 | x | + | 1244 | = | 1240 |
| 2 | x | = | 1240 | − | 1244 |
| 2 | x | = | - | 4 |
| x | = | - | 4 | ÷ | 2 |
| = | - | 4 | × | 1 2 |
| = | - | 2 | × | 1 |
| x | = | - | 2 |