(3y+12)/4=-((5y-1)/3-2)
3(3y+12)=-4(5y-1)+24 二边同乘12
9y+36=-20y+4+24
29y=28-36
29y=-8
y=-8/29
(3y+12)/4=(-24/29+12)/4
=-6/29+3
=81/87