Find the middle terms in the expansions of $\;\large ($$ 3 $$- \large\frac{x^3}{6})^7$

Question

$\begin{array}{1 1} T_4 = -\large\frac{105}{8}x^9 \qquad T_5 = \large\frac{35}{48}x^{12} \\ T_4 = \large\frac{105}{8}x^9 \qquad T_5 = \large\frac{35}{48}x^{12} \\ T_4 = \large\frac{105}{8}x^9 \qquad T_5 = -\large\frac{35}{48}x^{12} \\ T_4 = -\large\frac{105}{8}x^9 \qquad T_5 = -\large\frac{35}{48}x^{12}\end{array} $