| 9 | − | 40 | ÷ | 40 | × | ( | x | − | 40 | × | 90 | ÷ | 20 | ) | − | ( | 6 | − | 1 | ÷ | 4 | × | x | ) | = | 4 |
| 方程左边 = | 9 | − | 1 | ( | x | − | 40 | × | 90 | ÷ | 20 | ) | − | ( | 6 | − | 1 | ÷ | 4 | × | x | ) |
| 9 | − | 1 | ( | x | − | 40 | × | 90 | ÷ | 20 | ) | − | ( | 6 | − | 1 | ÷ | 4 | × | x | ) | = | 4 |
| 方程左边 = | 9 | − | 1 | x | + | 1 | × | 40 | × | 90 | ÷ | 20 | − | ( | 6 | − | 1 | ÷ | 4 | × | x | ) |
| = | 9 | − | 1 | x | + | 180 | − | ( | 6 | − | 1 | ÷ | 4 | × | x | ) |
| = | 189 | − | 1 | x | − | ( | 6 | − | 1 | ÷ | 4 | × | x | ) |
| = | 189 | − | 1 | x | − | 6 | + | 1 | ÷ | 4 | × | x |
| = | 189 | − | 1 | x | − | 6 | + | 1 4 | x |
| = | 183 | − | 3 4 | x |
| 183 | − | 3 4 | x | = | 4 |
| - | 3 4 | x | = | 4 | − | 183 |
| - | 3 4 | x | = | - | 179 |
| 179 | = | 3 4 | x |
3 4 | x | = | 179 |
| x | = | 179 | ÷ | 3 4 |
| = | 179 | × | 4 3 |
| x | = | 716 3 |
| x | = | 238.666667 |