| 7 | ( | 1 | − | 2 | x | ) | = | 3 | ( | 3 | x | + | 1 | ) | − | 21 |
| Left side of the equation = | 7 | × | 1 | − | 7 | × | 2 | x |
| = | 7 | − | 14 | x |
| 7 | − | 14 | x | = | 3 | ( | 3 | x | + | 1 | ) | − | 21 |
| Right side of the equation = | 3 | × | 3 | x | + | 3 | × | 1 | − | 21 |
| = | 9 | x | + | 3 | − | 21 |
| = | 9 | x | − | 18 |
| 7 | − | 14 | x | = | 9 | x | − | 18 |
| - | 14 | x | − | 9 | x | = | - | 18 | − | 7 |
| - | 23 | x | = | - | 18 | − | 7 |
| - | 23 | x | = | - | 25 |
| 25 | = | 23 | x |
| 23 | x | = | 25 |
| x | = | 25 | ÷ | 23 |
| = | 25 | × | 1 23 |
| x | = | 25 23 |
| x | = | 1.086957 |