| 3 | x | + | 25 | = | 45 | − | x |
| 3 | x | + | x | = | 45 | − | 25 |
| 4 | x | = | 45 | − | 25 |
| 4 | x | = | 20 |
| x | = | 20 | ÷ | 4 |
| = | 20 | × | 1 4 |
| = | 5 | × | 1 |
| x | = | 5 |
| 12 | + | 4 | x | × | 2 | = | 5 | x | + | 39 |
| 方程左边 = | 12 | + | 8 | x |
| 12 | + | 8 | x | = | 5 | x | + | 39 |
| 8 | x | − | 5 | x | = | 39 | − | 12 |
| 3 | x | = | 39 | − | 12 |
| 3 | x | = | 27 |
| x | = | 27 | ÷ | 3 |
| = | 27 | × | 1 3 |
| = | 9 | × | 1 |
| x | = | 9 |
| 4 | ( | 2 | x | + | 8 | ) | = | 40 |
| 方程左边 = | 4 | × | 2 | x | + | 4 | × | 8 |
| = | 8 | x | + | 32 |
| 8 | x | + | 32 | = | 40 |
| 8 | x | = | 40 | − | 32 |
| 8 | x | = | 8 |
| x | = | 8 | ÷ | 8 |
| = | 8 | × | 1 8 |
| = | 1 | × | 1 |
| x | = | 1 |