解方程. x-25%x=1519.6-70%x=5.6:x=.
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解:(1)x-25%x=15,
????????? 0.75x=15,
??? 0.75x÷0.75=15÷0.75,
????????????? x=20;
(2)19.6-70%x=5.6,
19.6-0.7x+0.7x=5.6+0.7x,
??????????19.6=5.6+0.7x,
????? 19.6-5.6=5.6+0.7x-5.6,
??????????? 14=0.7x,
??????????0.7x=14,
??? ?0.7x÷0.7=14÷0.7,
???????????? x=20;
(3):x=,
???? ÷x=.
???????? ?x=÷,
??????????x=3;
解析分析:(1)(2)根据等式性质解方程;
(3)先根据比与除法的关系化成除法算式,再根据除数=被除数÷商求解.
点评:解方程时要细心,注意把等号对齐.