| ( | 6 100 | × | 900 | + | x | ) | ÷ | ( | 900 | + | x | ) | = | 10 100 |
| Multiply both sides of the equation by: | ( | 900 | + | x | ) |
| ( | 6 100 | × | 900 | + | x | ) | = | 10 100 | ( | 900 | + | x | ) |
6 100 | × | 900 | + | x | = | 10 100 | ( | 900 | + | x | ) |
6 100 | × | 900 | + | x | = | 10 100 | × | 900 | + | 10 100 | x |
| 54 | + | x | = | 90 | + | 10 100 | x |
| x | − | 10 100 | x | = | 90 | − | 54 |
9 10 | x | = | 90 | − | 54 |
9 10 | x | = | 36 |
| x | = | 36 | ÷ | 9 10 |
| = | 36 | × | 10 9 |
| = | 4 | × | 10 |
| x | = | 40 |