20.5-（3.64+2.8）除于0.4=？

35.15

20.5-（3.64+2.8）/0.4
=20.5-6.44/0.4
=20.5-16.1
=4.4

20.5-（3.64+2.8）÷0.4
=20.5-(3.64 ÷0.4+2.8÷0.4)
=20.5-(9.1+7)
=20.5-9.1-7
=11.4-7
=4.4

计算器~~~
不开玩笑了。用20.5*0.4通分，然后分子相加然后再除0.4，我感觉这样挺简单的..

等于 20.5/0.4 -(3.64/0.4 + 2.8/0.4)
= 205/4 - ( 9.1 + 7)
= 51.25 - 16.1
=35.15

分步算式:

3.64+2.8=6.44

6.44÷0.4=16.1

20.5-16.1=4.4
答案应该是4.4,起码我是这样认为的,呵呵