优质解答
1：7/9 1/2
2：1/6--1/8 3/4+5/6
=3/18--2/18 =9/12+10/12
=1/18 =19/12
1--1/9 4/3+3/2
=8/9 =8/6+9/6
=17/6
4/5+1/3 3/2--1/3
=12/15+5/15 =9/6-2/6
=17/15 =7/6
4/5+3/10 2/3--2/7
=8/10+3/10 =14/21--6/21
=11/10 =8/21
3：1/8+1/10
=5/40+4/40
=9/40
1/8--1/10
=5/40--4/40
=1/40
1：7/9 1/2
2：1/6--1/8 3/4+5/6
=3/18--2/18 =9/12+10/12
=1/18 =19/12
1--1/9 4/3+3/2
=8/9 =8/6+9/6
=17/6
4/5+1/3 3/2--1/3
=12/15+5/15 =9/6-2/6
=17/15 =7/6
4/5+3/10 2/3--2/7
=8/10+3/10 =14/21--6/21
=11/10 =8/21
3：1/8+1/10
=5/40+4/40
=9/40
1/8--1/10
=5/40--4/40
=1/40