| 3 | x | ÷ | 5 | + | 5 | ( | 66 | − | x | ) | = | 78 |
| Left side of the equation = | 3 5 | x | + | 5 | ( | 66 | − | x | ) |
3 5 | x | + | 5 | ( | 66 | − | x | ) | = | 78 |
| Left side of the equation = | 3 5 | x | + | 5 | × | 66 | − | 5 | x |
| = | 3 5 | x | + | 330 | − | 5 | x |
| = | - | 22 5 | x | + | 330 |
| - | 22 5 | x | + | 330 | = | 78 |
| - | 22 5 | x | = | 78 | − | 330 |
| - | 22 5 | x | = | - | 252 |
| 252 | = | 22 5 | x |
22 5 | x | = | 252 |
| x | = | 252 | ÷ | 22 5 |
| = | 252 | × | 5 22 |
| = | 126 | × | 5 11 |
| x | = | 630 11 |
| x | = | 57.272727 |