①1/6x=1
x=6
②2x:1=1/6:5
1*（1/6）=2X*5
10X=1/6
X=1/60
③x-1/2=2x/5
(1-2/5)X=1/2
(3/5)X=1/2
X=5/6
④2/5x=12
x=12x(5/2)
X=30
⑤x-3/5x=3又1/2
(2/5)x=7/2
X=(7/2)*(5/2)
x=35/4
x=8又3/4