$a)_{}$ $(x-3)^3+3-x_{}$
$=(x-3)^3-(x-3)_{}$
$=(x-3) .[(x-3)^2-1 ] _{}$
$=(x-3)(x-3-1)(x-3+1)_{}$
$=(x-3)(x-4)(x-2)_{}$
$b)_{}$ $3x^3.(2y-3z)-15x.(2y-3z)^2_{}$
$=3x.(2y-3z). [ x^2-5.(2y-3z)] _{}$
$=3x.(2y-3z)(x^2-10y+15z)_{}$
$c)_{}$ $7x.(x-y)-(y-x)_{}$
$=7x.(x-y)+(x-y)_{}$
$=(x-y)(7x+1)_{}$
$d)_{}$ $3x.(x+2)+5.(-x-2)_{}$
$=3x.(x+2)-5.(x+2)_{}$
$=(3x-5)(x+2)_{}$