| ( | 4120 | + | 90 | x | ) | ÷ | ( | 97 2 | + | x | ) | = | 90 |
| Multiply both sides of the equation by: | ( | 97 2 | + | x | ) |
| ( | 4120 | + | 90 | x | ) | = | 90 | ( | 97 2 | + | x | ) |
| 4120 | + | 90 | x | = | 90 | ( | 97 2 | + | x | ) |
| 4120 | + | 90 | x | = | 90 | × | 97 2 | + | 90 | x |
| 4120 | + | 90 | x | = | 4365 | + | 90 | x |
| 90 | x | − | 90 | x | = | 4365 | − | 4120 |
| 0 | x | = | 4365 | − | 4120 |
| 0 | x | = | 245 |