| 25 | ( | 7 | − | 161 | a | + | 136 | ) | = | 0 |
| 方程左边 = | 25 | × | 7 | − | 25 | × | 161 | a | + | 25 | × | 136 |
| = | 175 | − | 4025 | a | + | 3400 |
| = | 3575 | − | 4025 | a |
| 3575 | − | 4025 | a | = | 0 |
| - | 4025 | a | = | 0 | − | 3575 |
| - | 4025 | a | = | - | 3575 |
| 3575 | = | 4025 | a |
| 4025 | a | = | 3575 |
| a | = | 3575 | ÷ | 4025 |
| = | 3575 | × | 1 4025 |
| = | 143 | × | 1 161 |
| a | = | 143 161 |
| a | = | 0.888199 |