| 3 | x | + | ( | 100 | − | x | ) | ÷ | 3 | × | 2 | = | 125 |
| 方程左边 = | 3 | x | + | ( | 100 | − | x | ) | × | 2 3 |
| 3 | x | + | ( | 100 | − | x | ) | × | 2 3 | = | 125 |
| 方程左边 = | 3 | x | + | 100 | × | 2 3 | − | x | × | 2 3 |
| = | 3 | x | + | 200 3 | − | x | × | 2 3 |
| = | 7 3 | x | + | 200 3 |
7 3 | x | + | 200 3 | = | 125 |
7 3 | x | = | 125 | − | 200 3 |
7 3 | x | = | 175 3 |
| x | = | 175 3 | ÷ | 7 3 |
| = | 175 3 | × | 3 7 |
| = | 25 | × | 1 |
| x | = | 25 |