简单的分数加减法1.4/9 +3/9 =7/9 7/10 －4/10 =3/10 2.7/8 5/7 4/9 7/10 3/5 5/8 4/

简单的分数加减法1.4/9 +3/9 =7/9 7/10 －4/10 =3/10 2.7/8 5/7 4/9 7/10 3/5 5/8 4/