the question is
determine the coefficient of the x^(-41) term in the expansion of (3x - (1/2x^2)^28
In the expansion of that you need to find the term $\displaystyle \dbinom{28}{k}
\left( {3x} \right)^k \left( {\frac{1}{{2x^2 }}} \right)^{28 - k} =\mathcal{C}x^{-41}$.
The value for $\displaystyle \mathcal{C}$ is what you are looking for.