a)3(x+5)-6(x-2)=4(x+2)-5(x-4)+1=
=3x+15-6x+12=4x+8-5x-20+1=
=-3x+27=-x-11=
=-3x=-11-27=
=-2x=-38=
=x=19
b) 15(x-1)+4(2-3x)=11-2(x+4)=
=15x-15+8-12x=11-2x-8=
=3x-7=3-2x=
=3x +2x=3+7
=5x=10=
=x=2
c)10(3-x)+6(x+3)=19+7(2x-1)=
=30-10x+6x+18=19+14x-7=
=48-4x=12+14x=
=-4x-14x=12-48=
=-18x=-36
x=2