| ( | 1 500 | + | 1 400 | + | a | + | 3 400 | + | 11 1000 | + | 1 80 | ) | × | 50 | = | 1 |
| 方程左边 = | 1 500 | × | 50 | + | 1 400 | × | 50 | + | a | × | 50 | + | 3 400 | × | 50 | + | 11 1000 | × | 50 | + | 1 80 | × | 50 |
| = | 1 10 | + | 1 8 | + | a | × | 50 | + | 3 8 | + | 11 20 | + | 5 8 |
| = | 71 40 | + | 50 | a |
71 40 | + | 50 | a | = | 1 |
| 50 | a | = | 1 | − | 71 40 |
| 50 | a | = | - | 31 40 |
| a | = | - | 31 40 | ÷ | 50 |
| = | - | 31 40 | × | 1 50 |
| a | = | - | 31 2000 |
| a | = | - 0.0155 |