To find the length of the rectangle in the new drawing with a scale factor of 1 box = 12 inches, we first need to determine the current length in inches.
Currently, with the scale factor of 1 box = 6 inches:
- The length of the rectangle is 10 boxes.
- Therefore, the length in inches is:
\[
10 \, \text{boxes} \times 6 \, \text{inches/box} = 60 \, \text{inches}
\]
Now, we want to determine how many boxes this length will occupy in the new scale where 1 box = 12 inches:
- To find the new length in boxes, we divide the length in inches by the new scale factor:
\[
\text{Length in boxes} = \frac{60 \, \text{inches}}{12 \, \text{inches/box}} = 5 \, \text{boxes}
\]
Therefore, the length of the boxes in the new drawing will be **5** boxes.
So, the correct response is:
**5**