1.14-7又 1/3-2又 1/2
=6又2/3-2又1/2
=4又1/6
2.13 又1/3-7又 1/6+14又 4/9
=6又1/6+14又4/9
=20又11/18
3.3又11/12-3/4+2又 5/6
=3又1/6+2又5/6
=6
4.11/2-4 又1/3+5 又5/6
=1又1/6+5又5/6
=7