7-(b+14)-2b;
3b-(18+b)+8;
(21-a)-(20-2a);
-(13+b)+(-b-13);
-(7-x)+4(x-5);
-9(y-4)-(12+y);

1) а) 2x-(2x+y)+y = 2x-2x-y+y = 0

     б) -a+(2a-b)+2b = -a+2a-b+2b = а+b

     в) 7-(b+14)-2b = 7-b-14-2b = -7-3b

     г) 3b-(18+b)+8 = 3b-18-b+8 = 2 -10 

2) а) 2(3-x)-(8+x) = 6-2x-8-x = -2-3x

     б) -4(y+5)+(12-y) = -4y-20+12-y = -5y -8

     в) -(7-x)+4(x-5) = -7+x+4x-20 = 5x-27

     г) -9(y-4)-(12+y) = -9y+36-12-y = 24 - 20y

7-(b+14)-2b=7-b-14-2b= -3b-73b-(18+b)+8=3b-18-b+8= 2b-10(21-a)-(20-2a)=21-a-20+2a=1a+1-(13+b)+(-b-13)=-13-b-b-13=-2b-26-(7-x)+5(x-5)=-7+x+5x-25=6x-32-9(y-4)-(12+y)=-9y+36-12-y=8y+24