To find the unit rate of cupcakes per box, you need to divide the total number of cupcakes by the number of boxes.
You have 12 cupcakes in 2 boxes, so:
\[ \text{Unit rate} = \frac{\text{Total cupcakes}}{\text{Total boxes}} = \frac{12 \text{ cupcakes}}{2 \text{ boxes}} = 6 \text{ cupcakes per box} \]
Thus, the unit rate is 6 cupcakes per box.