-(13+b)+(b-13)=
2(3,5-у)-3(1,4+у)=
-3(у-4)-(12+у)=

- (13+b) + (b-13)= - 13-b+b-13= -26
2(3.5-y)-3(1.4+y)= 7-2y - (4.2+3y)=7- 2y -4.2-3y= 2.8-5y
-3(y-4)-(12+y)= -3y+12-12-y=-4y