解:(1)x-
![](http://thumb.1010pic.com/pic5/latex/1154.png)
x=
![](http://thumb.1010pic.com/pic5/latex/4458.png)
x=
![](http://thumb.1010pic.com/pic5/latex/17341.png)
,
![](http://thumb.1010pic.com/pic5/latex/4458.png)
x÷
![](http://thumb.1010pic.com/pic5/latex/4458.png)
=
![](http://thumb.1010pic.com/pic5/latex/17341.png)
÷
![](http://thumb.1010pic.com/pic5/latex/4458.png)
,
x=
![](http://thumb.1010pic.com/pic5/latex/112.png)
.
(2)3.5-40%x=2.7
3.5-0.4x=2.7,
3.5-0.4x+0.4x=2.7+0.4x,
2.7+0.4x=3.5,
2.7-2.7+0.4x=3.5-2.7,
0.4x=0.8,
0.4x÷0.4=0.8÷0.4,
x=2.
分析:(1)先算出x-
![](http://thumb.1010pic.com/pic5/latex/1154.png)
x=
![](http://thumb.1010pic.com/pic5/latex/4458.png)
x,然后,利用等式的性质,两边同除以
![](http://thumb.1010pic.com/pic5/latex/4458.png)
,可以得出方程的解是:x=
![](http://thumb.1010pic.com/pic5/latex/112.png)
.
(2)先把百分数化为小数在计算,即40%x=0.4x,方程为:3.5-0.4x=2.7,我们要把方程两边同时加上0.4x,让x前面变成正号,便会得到方程2.7+0.4x=3.5.这时利用方程等式的性质,可以得出方程的解是:x=2.
点评:考查我们先把百分数化为小数,再利用等式的性质进行解方程.