| 25 | − | 2 | ( | a | − | 2 | ) | × | 5 | + | a | = | 0 |
| Left side of the equation = | 25 | − | 10 | ( | a | − | 2 | ) | + | a |
| 25 | − | 10 | ( | a | − | 2 | ) | + | a | = | 0 |
| Left side of the equation = | 25 | − | 10 | a | + | 10 | × | 2 | + | a |
| = | 25 | − | 10 | a | + | 20 | + | a |
| = | 45 | − | 9 | a |
| 45 | − | 9 | a | = | 0 |
| - | 9 | a | = | 0 | − | 45 |
| - | 9 | a | = | - | 45 |
| 45 | = | 9 | a |
| 9 | a | = | 45 |
| a | = | 45 | ÷ | 9 |
| = | 45 | × | 1 9 |
| = | 5 | × | 1 |
| a | = | 5 |