Does the stoichiometry effect the value of the equilibrium constant of an equilibrium reaction?
$$K_c = \mathrm{products \over reactants}$$ So this is done by multiplying the concentrations of the products and dividing by the concentrations of the reactants. The concentrations are put to the power of their coefficient. So in your problems at equilibrium $K_c$ would be:
\begin{align}
  K_c &amp;= \frac{[\ce{C}]^1}{[\ce{A}]^{\frac{1}{2}}[\ce{B}]^{\frac{3}{2}}}\tag1\\
  K_c &amp;= \frac{[\ce{C}]^2}{[\ce{A}]^1[\ce{B}]^3}\tag2\\
\end{align}

Note that $[\ce{A}]$ means concentration of $\ce{A}$.