| ( | 2 | A | − | 1 | ) | × | 150 | = | ( | 4 | + | 6 | ) | × | 140 |
| 方程左边 = | 2 | A | × | 150 | − | 1 | × | 150 |
| = | 300 | A | − | 150 |
| 300 | A | − | 150 | = | ( | 4 | + | 6 | ) | × | 140 |
| 方程右边 = | 4 | × | 140 | + | 6 | × | 140 |
| = | 560 | + | 840 |
| = | 1400 |
| 300 | A | − | 150 | = | 1400 |
| 300 | A | = | 1400 | + | 150 |
| 300 | A | = | 1550 |
| A | = | 1550 | ÷ | 300 |
| = | 1550 | × | 1 300 |
| = | 31 | × | 1 6 |
| A | = | 31 6 |
| A | = | 5.166667 |