-8(2x-y)-{7x-[6x+2y-(10x-8y)]}
=-16x+8y-[7x-(6x+2y-10x+8y)]
=-16x+8y-(7x-6x-2y+10x-8y)
=-16x+8y-7x+6x+2y-10x+8y
=-19x+18y
=18y-19x