G.P.: (-6,\ -3,\ -\dfrac{3}{2},\ \ldots)

(a=-6), (r=\dfrac{-3}{-6}=\dfrac{1}{2})

[ a_6 = ar^5 = -6\cdot\left(\dfrac{1}{2}\right)^5 = -6\cdot\dfrac{1}{32} = -\dfrac{3}{16} ]

Answer: (-\dfrac{3}{16})