练习题：

1. 1/2 + 1/4 - 3/8 = ?

2. 3/5 - 1/3 + 1/2 = ?

3. 2/3 + 1/6 - 2/9 = ?

4. 5/6 - 1/4 - 1/12 = ?

5. 1/3 + 1/2 - 1/6 - 1/12 = ?

解题思路：

分数加减混合运算需要分两种情况：

练习题解答：

1. 1/2 + 1/4 - 3/8 = 2/4 + 1/4 - 3/8 = 3/4 - 3/8 = 6/8 - 3/8 = 3/8

2. 3/5 - 1/3 + 1/2 = 9/15 - 5/15 + 6/15 = 10/15 = 2/3

3. 2/3 + 1/6 - 2/9 = 6/9 + 3/9 - 2/9 = 7/9

4. 5/6 - 1/4 - 1/12 = 10/12 - 3/12 - 1/12 = 6/12 = 1/2

5. 1/3 + 1/2 - 1/6 - 1/12 = 4/12 + 6/12 - 2/12 - 1/12 = 7/12