9/7-2/7+2/5的结果为7/5,计算方法:
=7/7+2/5
=1+2/5
=7/5
9/7-2/7+2/5的结果为7/5,计算方法:=7/7+2/5=5/5+2/5=7/5
原式=1+2/5=7/5