#(9x )/( x ^ { 2} - 9) div ( 8x - 48) / (2x + 6 ) #
=#(9x )/ ( x ^ { 2} - 9) xx (2x + 6 )/ ( 8x - 48)#
= # (9x )/(( x - 3)(x + 3)) xx (2(x +3) )/ ( 8(x - 6)) #
=#(9x )/(( x - 3)(x + 3))xx((x +3) )/ ( 4(x - 6))#
=#(9x )/(( x - 3))xx (1 )/ ( 4(x - 6))" "# cancelling the like terms #(x+3)# from #color(white)(wwwwwwwwwwwwwwww)#numerator and denominator.
=#(9x )/(( x - 3))xx(1 )/ ( 4(x - 6))#
=#(9x )/(4(x - 3)(x - 6))" "# you can leave it like this or:
=# (9x )/(4 ( x^2 - 9x + 18) )#