| 3 | x | + | ( | 100 | − | x | ) | × | 1 | ÷ | 3 | = | 100 |
| 方程左边 = | 3 | x | + | ( | 100 | − | x | ) | × | 1 3 |
| 3 | x | + | ( | 100 | − | x | ) | × | 1 3 | = | 100 |
| 方程左边 = | 3 | x | + | 100 | × | 1 3 | − | x | × | 1 3 |
| = | 3 | x | + | 100 3 | − | x | × | 1 3 |
| = | 8 3 | x | + | 100 3 |
8 3 | x | + | 100 3 | = | 100 |
8 3 | x | = | 100 | − | 100 3 |
8 3 | x | = | 200 3 |
| x | = | 200 3 | ÷ | 8 3 |
| = | 200 3 | × | 3 8 |
| = | 25 | × | 1 |
| x | = | 25 |