| ( | 300000000 | − | a | ) | ÷ | a | = | 8 5 |
| 方程两边同时乘以: | a |
| ( | 300000000 | − | a | ) | = | 8 5 | a |
| 300000000 | − | a | = | 8 5 | a |
| - | a | − | 8 5 | a | = | - | 300000000 |
| - | 13 5 | a | = | - | 300000000 |
| 300000000 | = | 13 5 | a |
13 5 | a | = | 300000000 |
| a | = | 300000000 | ÷ | 13 5 |
| = | 300000000 | × | 5 13 |
| a | = | 1500000000 13 |
| a | = | 115384615.384615004 |