| x | × | 3 | + | 1 | + | ( | 100 | − | x | ) | × | 4 | + | ( | 76 | − | x | ) | × | 2 | = | 400 |
| 方程左边 = | 3 | x | + | 1 | + | 100 | × | 4 | − | x | × | 4 | + | ( | 76 | − | x | ) | × | 2 |
| = | 3 | x | + | 1 | + | 400 | − | x | × | 4 | + | ( | 76 | − | x | ) | × | 2 |
| = | - | 1 | x | + | 401 | + | ( | 76 | − | x | ) | × | 2 |
| = | - | 1 | x | + | 401 | + | 76 | × | 2 | − | x | × | 2 |
| = | - | 1 | x | + | 401 | + | 152 | − | x | × | 2 |
| = | - | 3 | x | + | 553 |
| - | 3 | x | + | 553 | = | 400 |
| - | 3 | x | = | 400 | − | 553 |
| - | 3 | x | = | - | 153 |
| 153 | = | 3 | x |
| 3 | x | = | 153 |
| x | = | 153 | ÷ | 3 |
| = | 153 | × | 1 3 |
| = | 51 | × | 1 |
| x | = | 51 |