| ( | 940 | + | 4 5 | a | ) | ÷ | ( | 1268 | + | a | ) | = | 3 4 |
| 方程两边同时乘以: | ( | 1268 | + | a | ) |
| ( | 940 | + | 4 5 | a | ) | = | 3 4 | ( | 1268 | + | a | ) |
| 940 | + | 4 5 | a | = | 3 4 | ( | 1268 | + | a | ) |
| 940 | + | 4 5 | a | = | 3 4 | × | 1268 | + | 3 4 | a |
| 940 | + | 4 5 | a | = | 951 | + | 3 4 | a |
4 5 | a | − | 3 4 | a | = | 951 | − | 940 |
1 20 | a | = | 951 | − | 940 |
1 20 | a | = | 11 |
| a | = | 11 | ÷ | 1 20 |
| = | 11 | × | 20 |
| a | = | 220 |