解:(1)1-X=
![](http://thumb.1010pic.com/pic5/latex/14.png)
1-X+X=
![](http://thumb.1010pic.com/pic5/latex/14.png)
+X,
![](http://thumb.1010pic.com/pic5/latex/14.png)
+X=1,
![](http://thumb.1010pic.com/pic5/latex/14.png)
+X-
![](http://thumb.1010pic.com/pic5/latex/14.png)
=1-
![](http://thumb.1010pic.com/pic5/latex/14.png)
,
X=
![](http://thumb.1010pic.com/pic5/latex/335.png)
;
(2)28:X=7:75
7X=28×75,
7X÷7=28×75÷7,
X=300;
(3)7X-4.2=5.6
7X-4.2+4.2=5.6+4.2,
7X=9.8,
7X÷7=9.8÷7,
X=1.4;
(4)X:25=1.2:75
75X=25×1.2,
75X÷75=25×1.2÷75,
X=0.4.
分析:(1)(3)根据等式的基本性质解答;
(2)(4)解比例,先用比例的基本性质转化成方程再解答.
点评:本题主要考查解方程和解比例,注意格式.