| 5 | x | + | 6 | x | = | ( | 5 | x | − | 30 | ) | × | 3 |
| Left side of the equation = | 11 | x |
| 11 | x | = | ( | 5 | x | − | 30 | ) | × | 3 |
| Right side of the equation = | 5 | x | × | 3 | − | 30 | × | 3 |
| = | 15 | x | − | 90 |
| 11 | x | = | 15 | x | − | 90 |
| 11 | x | − | 15 | x | = | - | 90 |
| - | 4 | x | = | - | 90 |
| 90 | = | 4 | x |
| 4 | x | = | 90 |
| x | = | 90 | ÷ | 4 |
| = | 90 | × | 1 4 |
| = | 45 | × | 1 2 |
| x | = | 45 2 |
| x | = | 22.5 |