| 3 |
| 4 |
| 15 |
| 20 |
| 30 |
| 40 |
| 45 |
| 60 |
| 60 |
| 80 |
| 165 |
| 220 |
| 5 |
| 7 |
| 15 |
| 21 |
| 30 |
| 42 |
| 45 |
| 63 |
| 60 |
| 84 |
| 165 |
| 231 |
两个新分数的分母应相差11．
所以两个分母为：222和231；
原分数的分母是：220+2=222（或231-9=222），所以原来的分数为
| 165 |
| 222 |
故答案为
| 165 |
| 222 |
| b |
| a |
| b |
| a−2 |
| 3 |
| 4 |
| b |
| a+9 |
| 5 |
| 7 |
| b |
| a |
| 3 |
| 4 |
| 15 |
| 20 |
| 30 |
| 40 |
| 45 |
| 60 |
| 60 |
| 80 |
| 165 |
| 220 |
| 5 |
| 7 |
| 15 |
| 21 |
| 30 |
| 42 |
| 45 |
| 63 |
| 60 |
| 84 |
| 165 |
| 231 |
| 165 |
| 222 |
| 165 |
| 222 |