求未知数.
X-X=12-12%X=90.4X+0.06=1.
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解:(1)X-X=,
?????????? X=,
????????X×4=×4,
???????????? X=2.8;
(2)12-12%X=9,
12-0.12X+0.12X=9+0.12X,
???? ???? 12-9=9+0.12X-9,
???????3÷0.12=0.12X÷0.12,
???????????? X=25;
(3)0.4X+0.06=1,
0.4X+0.06-0.06=1-0.06,
???? 0.4X÷0.4=0.94÷0.4,
???????????? X=2.35.
解析分析:(1)先化简,再根据等式的性质,在方程两边同时乘上4求解,
(2)根据等式的性质,在方程两边同时加上0.12X,再减去9,最后除以0.12求解,
(3)根据等式的性质,在方程两边同时减去0.06,再除以0.4求解.
点评:本题考查了学生根据等式的性质解方程的能力,注意等号对齐.