解:(1)5X-2.7=
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,
5X-2.7+2.7=0.8+2.7,
5X=3.5,
5X÷5=3.5÷5,
X=0.7;
(2)X:3.6=
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:
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,
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X=3.6×
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,
0.8X=2.7,
0.8X÷0.8=2.7÷0.8,
X=3.375;
(3)5X-0.8×10=3.19,
5X-8=3.19,
5X-8+8=3.19+8,
5X=11.19,
5X÷5=11.19÷5,
X=2.238.
分析:(1)根据等式的性质,两边同加上2.7,再同除以5即可;
(2)先根据比例的性质改写成
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X=3.6×
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,即 0.8X=2.7,再根据等式的性质,两边同除以0.8即可;
(3)先求出0.8×10=8,原式变为5X-8=3.19,根据等式的性质,两边同加上8,再同除以5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、同减、同乘或同除以一个数(0除外),等式的左右两边仍相等;注意等号上下要对齐.