解方程. 70%x-10%x=15(1-25%)X=3x×(+)=.
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解:(1)70%x-10%x=15,
????? (70%-10%)x=15,
????????????? 0.6x=15,
?????????0.6x÷0.6=15÷0.6,
???????????????? x=25;
(2)(1-25%)X=3,
??????????0.75X=3,
??? 0.75X÷0.75=3÷0.75,
??????????????X=4;
(3)x×(+)=,
??????????? x=,
?????? x×=×,
?????????????? x=.
解析分析:(1)原式变为(70%-10%)x=15,即0.6x=15,根据等式的性质,两边同除以0.6即可;(2)原式变为0.75X=3,根据等式的性质,两边同除以0.75即可;(3)原式变为x=,根据等式的性质,两边同乘即可.
点评:此题考查了根据等式的性质解方程,即等式两边同加上或同减去、同乘上或同除以同一个数(0除外),两边仍相等.