| ( | 4120 | + | 90 | x | ) | ÷ | ( | 97 2 | + | x | ) | = | 87 |
| 方程两边同时乘以: | ( | 97 2 | + | x | ) |
| ( | 4120 | + | 90 | x | ) | = | 87 | ( | 97 2 | + | x | ) |
| 4120 | + | 90 | x | = | 87 | ( | 97 2 | + | x | ) |
| 4120 | + | 90 | x | = | 87 | × | 97 2 | + | 87 | x |
| 4120 | + | 90 | x | = | 8439 2 | + | 87 | x |
| 90 | x | − | 87 | x | = | 8439 2 | − | 4120 |
| 3 | x | = | 8439 2 | − | 4120 |
| 3 | x | = | 199 2 |
| x | = | 199 2 | ÷ | 3 |
| = | 199 2 | × | 1 3 |
| x | = | 199 6 |
| x | = | 33.166667 |