| 1100 | ÷ | ( | 280 | + | A | ) | = | 11 5 |
| Multiply both sides of the equation by: | ( | 280 | + | A | ) |
| 1100 | = | 11 5 | ( | 280 | + | A | ) |
| 1100 | = | 11 5 | × | 280 | + | 11 5 | A |
| 1100 | = | 616 | + | 11 5 | A |
| - | 11 5 | A | = | 616 | − | 1100 |
| - | 11 5 | A | = | - | 484 |
| 484 | = | 11 5 | A |
11 5 | A | = | 484 |
| A | = | 484 | ÷ | 11 5 |
| = | 484 | × | 5 11 |
| = | 44 | × | 5 |
| A | = | 220 |