| ( | 13 | + | ( | x | − | 3 | ) | ) | − | ( | 8 | + | ( | x | − | 3 | ) | ) | = | 4 5 | x |
| 方程左边 = | 13 | + | ( | x | − | 3 | ) | − | ( | 8 | + | ( | x | − | 3 | ) | ) |
| = | 13 | + | x | − | 3 | − | ( | 8 | + | ( | x | − | 3 | ) | ) |
| = | 10 | + | x | − | ( | 8 | + | ( | x | − | 3 | ) | ) |
| = | 10 | + | x | − | 8 | − | ( | x | − | 3 | ) |
| = | 2 | + | x | − | ( | x | − | 3 | ) |
| = | 2 | + | x | − | x | + | 3 |
| = | 5 | + | 0 | x |
| 5 | = | 4 5 | x |
| - | 4 5 | x | = | - | 5 |
| 5 | = | 4 5 | x |
4 5 | x | = | 5 |
| x | = | 5 | ÷ | 4 5 |
| = | 5 | × | 5 4 |
| x | = | 25 4 |
| x | = | 6.25 |