a)
[tex](x+5)-(3x+2)=x+5-3x-2=x-3x+5-2=\\\\=-2x+3=-2\cdot3+3=-6+3=-(6-3)=-3[/tex]
b)
[tex]-2x-(5x+6)=-2x-5x-6=-7x-6=\\\\=-7\cdot3-6=-21-6=-(21+6)=-27[/tex]
c)
[tex]-(x+2)+3x=-x-2+3x=-x+3x-2=\\\\=2x-2=2\cdot3-2=6-2=4[/tex]
d)
[tex]-(5x-6)+(2x-3)=-5x+6+2x-3=-5x+2x+6-3=\\\\=-3x+3=-3\cdot3+3=-9+3=-(9-3)=-6[/tex]