| ( | 399 | ÷ | 20 | ) | ( | 399 | ÷ | 20 | ) | = | 20 | x |
| Left side of the equation = | 399 | ÷ | 20 | × | ( | 399 | ÷ | 20 | ) |
| = | 399 20 | ( | 399 | ÷ | 20 | ) |
| = | 399 20 | × | 399 | ÷ | 20 |
| = | 159201 400 |
159201 400 | = | 20 | x |
| - | 20 | x | = | - | 159201 400 |
159201 400 | = | 20 | x |
| 20 | x | = | 159201 400 |
| x | = | 159201 400 | ÷ | 20 |
| = | 159201 400 | × | 1 20 |
| x | = | 159201 8000 |
| x | = | 19.900125 |