To convert the length from a scale of 1 box = 6 meters to a scale of 1 box = 3 meters, we need to consider how the scaling affects the dimensions.
In the original scale, the rectangle is 7 boxes long. Since 1 box represents 6 meters, the length in meters is calculated as follows:
\[ \text{Length in meters} = 7 , \text{boxes} \times 6 , \text{meters/box} = 42 , \text{meters} \]
Now, to find the equivalent length in boxes when using the new scale of 1 box = 3 meters, we divide the total length in meters by the new scale:
\[ \text{Length in boxes} = \frac{42 , \text{meters}}{3 , \text{meters/box}} = 14 , \text{boxes} \]
Therefore, the length in boxes of the new drawing will be 14.
The correct response is 14.