| 5 | I | × | 1 | + | 15 | I | × | 3 | − | 180 | = | 0 |
| 方程左边 = | 5 | I | + | 45 | I | − | 180 |
| = | 50 | I | − | 180 |
| 50 | I | − | 180 | = | 0 |
| 50 | I | = | 0 | + | 180 |
| 50 | I | = | 180 |
| I | = | 180 | ÷ | 50 |
| = | 180 | × | 1 50 |
| = | 18 | × | 1 5 |
| I | = | 18 5 |
| I | = | 3.6 |
| 10 | I | × | 2 | + | 15 | I | × | 3 | − | 80 | = | 0 |
| 方程左边 = | 20 | I | + | 45 | I | − | 80 |
| = | 65 | I | − | 80 |
| 65 | I | − | 80 | = | 0 |
| 65 | I | = | 0 | + | 80 |
| 65 | I | = | 80 |
| I | = | 80 | ÷ | 65 |
| = | 80 | × | 1 65 |
| = | 16 | × | 1 13 |
| I | = | 16 13 |
| I | = | 1.230769 |