139 | = | 42 | + | 57 | + | 88 | − | ( | 30 | + | 12 | + | 30 | + | 12 | + | 30 | + | 12 | ) | + | 12 | + | x |
方程右边 = | 199 | − | ( | 30 | + | 12 | + | 30 | + | 12 | + | 30 | + | 12 | ) | + | x |
139 | = | 199 | − | ( | 30 | + | 12 | + | 30 | + | 12 | + | 30 | + | 12 | ) | + | x |
方程右边 = | 199 | − | 30 | − | 12 | − | 30 | − | 12 | − | 30 | − | 12 | + | x |
= | 73 | + | x |
139 | = | 73 | + | x |
- | x | = | 73 | − | 139 |
- | x | = | - | 66 |
66 | = | x |
x | = | 66 |