(x-y)+x=x-y+x=x+x-y=2x-y
(-a-7)=-7,3-a-7=-a-7-7=-a-14
(-x-k+0,3)=-k+3+x+k-0,3=-k+k+x-x+3-0,3=2.7
(-4,5a+x)=8,5a-x+0,5a-4,5a+x=-4,5a+x+x-8,5a+0,5a-4,5a=-3,5a+x-8,5a
(x-y)+x=x-y+x=x+x-y=2x-y
(-a-7)=-7,3-a-7=-a-7-7=-a-14
(-x-k+0,3)=-k+3+x+k-0,3=-k+k+x-x+3-0,3=2.7
(-4,5a+x)=8,5a-x+0,5a-4,5a+x=-4,5a+x+x-8,5a+0,5a-4,5a=-3,5a+x-8,5a