3^x=2,12^y=8∴ x=log3(2),y=log12(8)∴ 1/x=log2(3),1/y=log8(12)∴ 1/x-3/y=log2(3)-3log8(12)=log2(3)-log2³(12³)=log2(3)-log2(12)=log2(3/12)=log2(1/4)=-2