3[x-2(x-a/3)]=4x
3(x-2x+2a/3)=4x
-3x+2a=4x
7x=2a
x=2a/7
3x+a/12-1-5x/8=1
19/8x=2+a/12
x=16/19+96/19a
有相同的解
所以2a/7=16/19+96/19a
-634/133a=16/19
a=-56/317