-(7-х)+(3х-14)=-7+х+3х-14=-21+4х
-(4+х)-(2х-8)=-х-4-2х+8=-3х+4
(21-а)-(20-2а)=21-а-20+2а=1+а
-(13+в)+(-в-13)=-13-в-в-13=-26-2в=26+2в
2*(3-х)-(8+х)=6-2х-(8+х)=6-2х-8-х=-2-3х
-4(у+5)+(12-у)=-4у-20+12-у=-5у-8=5у+8
-(7-х)+4(х-5)=-7+х+4х-20=-27+5х
-9(у-4)-(12+у)=-9у+36-12-у=-10у+24