Explain an error problem in each of the following:

c) 8 3/8-6 1/4=2 2/4, 5 3/8-2 2/3=3 1/5, 2 2/7-1 1/3=1 1/4

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

5 9/24 - 2 16/24 = 129/24 - 64/24 = ?

2 2/7 - 1 1/3 = 2 6/21 - 1 7/21 = ?