3.85: Binomial expansion first four terms

It is given that the first four terms, in ascending powers of $x$, in the expansion of $\left(1-\dfrac{x}{2}\right)^{n}$ can be written in the form $1-8x+px^{2}+qx^{3}$, where $n$, $p$ and $q$ are integers. Find the values of $n$, $p$ and $q$.

Find the term independent of $x$ in the expansion of $\left(\dfrac{2}{x^{2}}+\dfrac{x}{3}\right)^{6}$, giving your answer as a rational number.