(5x^3) (-3x^-3)
(5x3)(-3x-3) = (5)(x3)(-3)(x-3) = (5)(-3)(x3)(x-3) = -15(x3+(-3)) = -15x0 = -15(1) = -15
Or you can just write it like this:
\(\frac{(5)(x^3)(-3)}{x^3} = (5)(-3) = -15\)