3/5+1/4-7/10
=17/20-14/20
=3/20
14-1/2-2/7
=13又1/2-2/7
=13又3/14
5/8-(3/4-1/3)
=5/8-5/12
=5/24
5/8+1/9+2/9+11/8
=(5/8+11/8)+(1/9+2/9)
=2+1/3
=2又1/3
3/5+1/4-7/10
=17/20-14/20
=3/20
14-1/2-2/7
=13又1/2-2/7
=13又3/14
5/8-(3/4-1/3)
=5/8-5/12
=5/24
5/8+1/9+2/9+11/8
=(5/8+11/8)+(1/9+2/9)
=2+1/3
=2又1/3