3/4 5/6
=9/12 10/12
=19/12
2/3-1/4
=8/12-3/12
=5/12
4/5 11/15 3/10
=24/30 22/30 9/30
=55/30
7-5/7
=6 7/7-5/7
=6 2/7
1/2 2/3
=3/6 4/6
=7/6
6-(3/4-2/5)
=6-3/4 2/5
=6-15/20 8/20
=4 40/20-23/20
=4 17/20
4 17/20的意思是4又20分之17
额我好像全部调转了,知己该会它