解:(1)1.4-5x=3×
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,
1.4-5x+5x=0.4+5x,
1.4=0.4+5x,
1.4-0.4=0.4+5x-0.4,
1=5x,
1÷5=5x÷5,
x=
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;
(2)x-
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x=2.4,
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x=2.4,
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x÷
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=2.4÷
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,
x=7.2;
(3)2.4×5+5.6x=68,
12+5.6x=68,
12+5.6x-12=68-12,
5.6x=56,
5.6x÷5.6=56÷5.6,
x=10.
分析:(1)先化简方程,再依据等式的性质,方程两边同时减去5x,再同时减去0.4,最后除以5求解;
(2)先化简方程,再依据等式的性质,方程两边同时除以
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求解;
(3)先化简方程,再依据等式的性质,方程两边同时减去12,再同时除以5.6求解.
点评:本题主要考查解方程,根据等式的性质进行解答即可.