| 130 | − | 2 | ÷ | 3 | × | a | − | ( | 130 | − | a | ) | × | 3 | ÷ | 4 | = | 40 |
| 方程左边 = | 130 | − | 2 3 | a | − | ( | 130 | − | a | ) | × | 3 4 |
| 130 | − | 2 3 | a | − | ( | 130 | − | a | ) | × | 3 4 | = | 40 |
| 方程左边 = | 130 | − | 2 3 | a | − | 130 | × | 3 4 | + | a | × | 3 4 |
| = | 130 | − | 2 3 | a | − | 195 2 | + | a | × | 3 4 |
| = | 65 2 | + | 1 12 | a |
65 2 | + | 1 12 | a | = | 40 |
1 12 | a | = | 40 | − | 65 2 |
1 12 | a | = | 15 2 |
| a | = | 15 2 | ÷ | 1 12 |
| = | 15 2 | × | 12 |
| = | 15 | × | 6 |
| a | = | 90 |