| ( | 10 | + | x | ) | ÷ | ( | 21 | + | x | ) | = | 11 20 |
| Multiply both sides of the equation by: | ( | 21 | + | x | ) |
| ( | 10 | + | x | ) | = | 11 20 | ( | 21 | + | x | ) |
| 10 | + | x | = | 11 20 | ( | 21 | + | x | ) |
| 10 | + | x | = | 11 20 | × | 21 | + | 11 20 | x |
| 10 | + | x | = | 231 20 | + | 11 20 | x |
| x | − | 11 20 | x | = | 231 20 | − | 10 |
9 20 | x | = | 231 20 | − | 10 |
9 20 | x | = | 31 20 |
| x | = | 31 20 | ÷ | 9 20 |
| = | 31 20 | × | 20 9 |
| = | 31 | × | 1 9 |
| x | = | 31 9 |
| x | = | 3.444444 |