3道简便计算,
问题描述：
3道简便计算,
①3/5+3/10+1/2 ②5/6+7/9+1/6 ③2/3-2/9+1/3-7/9
答
1.原式=3/5+3/10+5/10
=3/5+4/5=7/5
2.原式=1+7/9=16/9
3.原式=(2/3+1/3)-(2/9+7/9)
=1-1=0