| 310 | = | 80 | a | × | 1 | ÷ | ( | 80 | + | 400 | ) |
| Multiply both sides of the equation by: | ( | 80 | + | 400 | ) |
| 310 | ( | 80 | + | 400 | ) | = | 80 | a | × | 1 |
| 310 | × | 80 | + | 310 | × | 400 | = | 80 | a | × | 1 |
| 24800 | + | 124000 | = | 80 | a |
| 148800 | = | 80 | a |
| - | 80 | a | = | - | 148800 |
| 148800 | = | 80 | a |
| 80 | a | = | 148800 |
| a | = | 148800 | ÷ | 80 |
| = | 148800 | × | 1 80 |
| = | 1860 | × | 1 |
| a | = | 1860 |