64.7—3.89+13.69,怎样使计算简便
问题描述：
64.7—3.89+13.69,怎样使计算简便
急救
答
64.7—3.89+13.69
=64.5+0.2+13.69-3.89
=64.5+(13.89-3.89)
=64.5+10
=74.5