If one of the terms of the binomial expression (x+y-3z)^n is A*x^3*y^4*z^2 , what is n ?

$n = 9$ and $A = 11340$
In ${\left(x + y - 3 z\right)}^{9}$ appears all the ${x}^{a} {y}^{b} {z}^{c}$ products such that $a + b + c = 9$