x/x-3减x+6/x^2-3x加3/x
=[x*x-(x+6)+3(x-3)]/x(x-3)
=(x^2-x-6+3x-9)/x(x-3)
=(x^2+2x-15)/x(x-3)
=(x+5)(x-3)/x(x-3)
=(x+5)/x
所以原式
=13/3