The mechanical advantage (MA) of a wedge is typically determined by the formula:
\[ \text{MA} = \frac{\text{length of the wedge}}{\text{width of the wedge}} \]
So, among the options you provided, the closest correct equation is:
\[ \text{MA} = \text{length} / \text{width} \]
Thus, the correct answer is:
MA = length / width.