| ( | 10000 | − | 10001 5 | ) | ÷ | ( | a | − | 10001 5 | ) | = | - | 4 |
| Multiply both sides of the equation by: | ( | a | − | 10001 5 | ) |
| ( | 10000 | − | 10001 5 | ) | = | - | 4 | ( | a | − | 10001 5 | ) |
| 10000 | − | 10001 5 | = | - | 4 | ( | a | − | 10001 5 | ) |
| 10000 | − | 10001 5 | = | - | 4 | a | + | 4 | × | 10001 5 |
| 10000 | − | 10001 5 | = | - | 4 | a | + | 40004 5 |
39999 5 | = | - | 4 | a | + | 40004 5 |
| 4 | a | = | 40004 5 | − | 39999 5 |
| 4 | a | = | 1 |
| a | = | 1 | ÷ | 4 |
| = | 1 | × | 1 4 |
| a | = | 1 4 |
| a | = | 0.25 |