求未知数x. (1)0.6x+15%x-1.4=3.1(2)2.4:3.2=.
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解:(1)0.6x+15%x-1.4=3.1,
???????????? 0.75x-1.4=3.1,
???????? 0.75x-1.4+1.4=3.1+1.4,
???????????????? 0.75x=4.5,
?????????? 0.75x÷0.75=4.5÷0.75,
???????????????????? x=6;
(2)2.4:3.2=,
?????????3.2x=2.4×20,
???23.2x÷3.2=48÷3.2,
??????????? x=15.
解析分析:(1)先化简方程,再根据等式的性质,在方程两边同时减去1.4,再同时除以0.75求解,
(2)先依据比例的基本性质,化简等式,再根据等式的性质,在方程两边同时除以3.2求解.
点评:本题考查了学生根据等式的性质解答方程的能力,注意等号对齐.