x=-3
x·(x-4)·(x+4) - (x+3)·(x^2-6x+9) + 5x^3 y^2÷x^2 y^2
= x(x^2-16) - (x+3)(x-3)^2 + 5x
= x^3 -16x - (x^2-9)(x+3) + 5x
= x^3 -16x - (x^3-9x+3x^2-27) + 5x
= x^3 -16x - x^3+9x-3x^2+27 + 5x
= -3x^2 - 2x + 27
= -3*(-3)^2 -2*(-3) +27
= -27 +6 +27
= 6