Let's perform the synthetic division
#color(white)(aaaa)##3##color(white)(aaaaa)##|##color(white)(aaaa)##9##color(white)(aaaaaa)##-19##color(white)(aaaaaa)##-28##color(white)(aaaa)##12#
#color(white)(aaaaaaaaaaaa)#_________
#color(white)(aaaa)##color(white)(aaaaaaa)##|##color(white)(aaaa)##color(white)(aaaaaaaa)##27##color(white)(aaaaaaa)##24##color(white)(aaa)##-12#
#color(white)(aaaaaaaaaaaa)#________
#color(white)(aaaa)##color(white)(aaaaaaa)##|##color(white)(aaaa)##9##color(white)(aaaaaaaa)##8##color(white)(aaaaaa)##-4##color(white)(aaaaaa)##color(red)(0)#
#(9x^3-19x^2-28x+12)/(x-3)=(9x^2+8x-4)#
The remainder is #=0# and the quotient is #=9x^2+8x-4#