解方程.
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(1)
x=5 12
,7 8
x×5 12
=12 5
×7 8
,12 5
x=2.1;
(2)x+
=1 6
,8 5
x+
-1 6
=1 6
-8 5
,1 6
x=
;43 30
(3)
÷x=30 7
,2 28
÷x×x=30 7
×x,1 14
x=1 14
,30 7
x×14=1 14
×14,30 7
x=60;
(4)50%x+30%x=8,
(50%+30%)x=8,
0.8x=8,
0.8x÷0.8=8÷0.8,
x=10;
(5)x-20%x=40,
(1-20%)x=40,
0.8x=40,
0.8x÷0.8=40÷0.8,
x=50.