| 3 | − | 30 | a | = | ( | 3 | − | 30 | ( | 3 | − | 20 | a | ) | ÷ | 20 | ) | × | 2 |
| Right side of the equation = | 3 | × | 2 | − | 30 | ( | 3 | − | 20 | a | ) | ÷ | 20 | × | 2 |
| = | 6 | − | 3 | ( | 3 | − | 20 | a | ) |
| = | 6 | − | 3 | × | 3 | + | 3 | × | 20 | a |
| = | 6 | − | 9 | + | 60 | a |
| = | - | 3 | + | 60 | a |
| 3 | − | 30 | a | = | - | 3 | + | 60 | a |
| - | 30 | a | − | 60 | a | = | - | 3 | − | 3 |
| - | 90 | a | = | - | 3 | − | 3 |
| - | 90 | a | = | - | 6 |
| 6 | = | 90 | a |
| 90 | a | = | 6 |
| a | = | 6 | ÷ | 90 |
| = | 6 | × | 1 90 |
| = | 1 | × | 1 15 |
| a | = | 1 15 |
| a | = | 0.066667 |