D is incorrect
When you subtract fractions, the denominators need to be the same:
A)
4/6 - 2/4 = 1/6
8/12 - 6/12 = 2/12
2/12 = 1/6
B)
3/4 - 3/8 = 3/8
6/8 - 3/8 = 3/8
C)
4/5 - 3/4 = 1/20
16/20 - 15/20 = 1/20
D)
9/12 - 3/4 = 6/8
18/24 - 18/24 = 0
6/8 is not equal to 0
