| 40 | − | ( | 3 | a | + | 1 | ) | = | 60 | + | 2 | a | − | 1 |
| Left side of the equation = | 40 | − | 3 | a | − | 1 |
| = | 39 | − | 3 | a |
| 39 | − | 3 | a | = | 60 | + | 2 | a | − | 1 |
| Right side of the equation = | 59 | + | 2 | a |
| 39 | − | 3 | a | = | 59 | + | 2 | a |
| - | 3 | a | − | 2 | a | = | 59 | − | 39 |
| - | 5 | a | = | 59 | − | 39 |
| - | 5 | a | = | 20 |
| - | 20 | = | 5 | a |
| 5 | a | = | - | 20 |
| a | = | - | 20 | ÷ | 5 |
| = | - | 20 | × | 1 5 |
| = | - | 4 | × | 1 |
| a | = | - | 4 |