5/4-2/7-5/7
=5/4-(2/7+5/7)
=1又1/4-1
=1/4
7/6-(2/3+1/6)
=7/6-1/6-2/3
=1-2/3
=1/3
1-3/4+1/4
=1-(3/4-1/4)
=1-1/2
=1/2
5/8+1/4-1/2-1/4
=(5/8-1/2)+(1/4-1/4)
=5/8-4/8
=1/8
5/4-2/7-5/7
=5/4-(2/7+5/7)
=1又1/4-1
=1/4
7/6-(2/3+1/6)
=7/6-1/6-2/3
=1-2/3
=1/3
1-3/4+1/4
=1-(3/4-1/4)
=1-1/2
=1/2
5/8+1/4-1/2-1/4
=(5/8-1/2)+(1/4-1/4)
=5/8-4/8
=1/8