| ( | 3 | ÷ | 7 | ) | ÷ | ( | 5 | ÷ | 21 | ) | = | x | ÷ | 5 |
| Multiply both sides of the equation by: | ( | 5 | ÷ | 21 | ) |
| ( | 3 | ÷ | 7 | ) | = | x | ÷ | 5 | × | ( | 5 | ÷ | 21 | ) |
| 3 | ÷ | 7 | = | x | ÷ | 5 | × | ( | 5 | ÷ | 21 | ) |
| 3 | ÷ | 7 | = | x | ÷ | 5 | × | 5 | ÷ | 21 |
3 7 | = | x | × | 1 21 |
| - | 1 21 | x | = | - | 3 7 |
3 7 | = | 1 21 | x |
1 21 | x | = | 3 7 |
| x | = | 3 7 | ÷ | 1 21 |
| = | 3 7 | × | 21 |
| = | 3 | × | 3 |
| x | = | 9 |