(5x+3y)+(2x-7y+6)
(8x+7y-9)-(-5x-7y+4)
3(2x-3y+7)-2(-6x-y+3)
0.4[3x-(5y-7y)]+2(3x-y-4)
3/1(x-2y+1)-5/1(2x+y-1)