| 210 | = | 80 | a | × | 1 | ÷ | ( | 80 | + | 600 | ) |
| Multiply both sides of the equation by: | ( | 80 | + | 600 | ) |
| 210 | ( | 80 | + | 600 | ) | = | 80 | a | × | 1 |
| 210 | × | 80 | + | 210 | × | 600 | = | 80 | a | × | 1 |
| 16800 | + | 126000 | = | 80 | a |
| 142800 | = | 80 | a |
| - | 80 | a | = | - | 142800 |
| 142800 | = | 80 | a |
| 80 | a | = | 142800 |
| a | = | 142800 | ÷ | 80 |
| = | 142800 | × | 1 80 |
| = | 1785 | × | 1 |
| a | = | 1785 |