90 100 | ( | ( | 1 | + | 20 100 | ) | x | + | ( | 2200 | − | x | ) | ( | 1 | + | 15 100 | ) | ) | − | 2200 | = | 131 |
| 方程左边 = | 90 100 | ( | 1 | + | 20 100 | ) | x | + | 90 100 | ( | 2200 | − | x | ) | ( | 1 | + | 15 100 | ) | − | 2200 |
| = | 90 100 | × | 1 | x | + | 90 100 | × | 20 100 | x | + | 90 100 | ( | 2200 | − | x | ) | ( | 1 | + | 15 100 | ) | − | 2200 |
| = | 9 10 | x | + | 9 50 | x | + | 90 100 | ( | 2200 | − | x | ) | ( | 1 | + | 15 100 | ) | − | 2200 |
| = | 27 25 | x | + | 90 100 | ( | 2200 | − | x | ) | ( | 1 | + | 15 100 | ) | − | 2200 |
| = | 27 25 | x | + | 90 100 | × | 2200 | ( | 1 | + | 15 100 | ) | − | 90 100 | x | ( | 1 | + | 15 100 | ) | − | 2200 |
| = | 27 25 | x | + | 1980 | ( | 1 | + | 15 100 | ) | − | 90 100 | x | ( | 1 | + | 15 100 | ) | − | 2200 |
| = | 27 25 | x | + | 1980 | × | 1 | + | 1980 | × | 15 100 | − | 90 100 | x | ( | 1 | + | 15 100 | ) | − | 2200 |
| = | 27 25 | x | + | 1980 | + | 297 | − | 90 100 | x | ( | 1 | + | 15 100 | ) | − | 2200 |
| = | 27 25 | x | + | 77 | − | 90 100 | x | ( | 1 | + | 15 100 | ) |
| = | 27 25 | x | + | 77 | − | 90 100 | x | × | 1 | − | 90 100 | x | × | 15 100 |
| = | 27 25 | x | + | 77 | − | 9 10 | x | − | 27 200 | x |
| = | 9 200 | x | + | 77 |
9 200 | x | + | 77 | = | 131 |
9 200 | x | = | 131 | − | 77 |
9 200 | x | = | 54 |
| x | = | 54 | ÷ | 9 200 |
| = | 54 | × | 200 9 |
| = | 6 | × | 200 |
| x | = | 1200 |