tatianamihmar -15-4х= -8х-45
8х-4х=15-45
4х=-30
х=-30:4
х= - 7,5=(-7_1/2)

-8х-17=3х-105
-8х-3х=-105+17
-11х= -88
х= -88:(-11)
х=8

2(у+3)=21-3у
2у+6=21-3у
2у+3у=21-6
5у=15
у=15:5
у=3

(2-с)+3(с-3)= -13
2-с+3с-9=-13
2с=9-2-13
2с=-6
с=-6:2
с=-3

-31(1-3b)-12=12
-3+9b-12=12
9b=12+12+3
9b=27
b=27:9
b=3